There is something about the very phrase "learned society" that evokes dark wooden panelling, comfortable leather armchairs - and men too elderly to haul themselves out of them.

And it isn't hard to find examples that justify these cliches. One society responded to a request for information with the admission that it was "a bit of a dinosaur ... though we have managed to get our average membership age to under 70 over the past years. We have also entered the electronic age with a website and a mailing list (among quite a bit of protest from members!)."

Many of Britain's leading learned societies date back well into the 19th century or before - the Society of Antiquaries was founded in 1707 - and are understandably proud of their history and, in many cases, historic buildings. But what if Victorian heritage and decor is also a burden, sending rather the wrong messages for the present day?

The Institution of Mechanical Engineers (IMechE) was dreamt up by George Stephenson and friends in a pub in Birmingham. The first meeting was held in 1847. The current headquarters was built in 1899 in the very heart of London - then virtually the heart of the world - in Birdcage Walk, midway between Parliament and Buckingham Palace. One of the "big three", along with "the Civils" and "the Electricals", IMechE certainly stakes a major claim for engineering close to government and the City.

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First impressions are pretty imposing. The facade, with its Grecian columns, looks straight out at the Treasury and St James's Park. Inside, one finds lots of dark wood, models of early engines, a plush lecture theatre with portraits of past presidents looking down from the walls, an original Victorian library and, downstairs, the Marble Room, once used for smoking. Meeting rooms pay tribute to the great names of British engineering, with photographs and panels commemorating their achievements.

It is beautiful: perfect for receptions but also redolent of a lost era. Visitors are left in no doubt that mechanical engineering is worthy and important - but not very sexy or exciting. Depressingly, but perhaps inevitably, one has to search hard to spot a single woman amid the hundreds of images of grey men.

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What is now the Royal Commonwealth Society (RCS) was founded 140 years ago and obtained premises in "a pokey hole" above a shirt shop on The Strand. Alongside more scholarly goals, according to the first chairman, Viscount Bury, the aim was "to provide a meeting place for gentlemen interested in colonial and Indian affairs". A royal charter was granted in 1869, and a clubhouse was opened in 1885. And the name slowly evolved: from the Colonial Society to the Royal Colonial Society, the Royal Colonial Institute and then the Royal Empire Society.

The Royal Asiatic Society (RAS), created in 1823, was also almost parodically colonial in its early days. The lavish treasures it owns, according to the society's brochure, include "the unique collection of Malay and Javanese manuscripts of Sir Stamford Raffles; the manuscripts, paintings and scrolls relating to Rajasthan, collected by Colonel James Tod, first librarian of the Society; the collection of Tibetan manuscripts, many presented by Brian Houghton Hodgson, 'the father of Himalayan studies'".

So how have these institutions adapted and reinvented themselves, building on their traditions without being constrained by them? Learned societies have a number of functions: providing a congenial meeting place; sponsoring lectures and journals; accrediting degrees and other qualifications; acting as the voice of a profession or academic discipline to government, media and the general public. Yet few can afford to do everything, and most have to make tough choices about where to focus. And there seem to be almost as many solutions as there are societies.

Asked about its priorities, the Royal Institute of Philosophy gave a suitably philosophical answer: "We do not represent academic philosophers. Instead, we exist to bring philosophy to the wider world, the world outside academe. If anything, we just try to have philosophy itself heard, rather than the voices of individual philosophers or the voice of the profession (if there is such a thing ... I kind of hope there isn't)."

The Royal Empire Society, unsurprisingly, was "rebranded" as the Royal Commonwealth Society in 1958. It now describes itself as "the engine room of Commonwealth ideas ... offering a forum for the debate, research and development of Commonwealth thinking on key international issues". Its admirably 21st-century ideals include "celebrating diversity, inspiring young people and serving as a practical expression of living multiculturalism".

So how has the RCS put behind it the age of colonial gentlemen scholars? Now usually known as the "Royal Commonwealth Society at the Commonwealth Club", it occupies a glitzy modern building near the Embankment, with a 250-seat auditorium, business facilities, exhibition space, restaurant, members' lounge and bar. Only a single section of the old dark Canadian timber panelling has been retained as a kind of gentle tribute to the past.

The club acts as "a magnet for influential figures from politics, diplomacy, the media and arts" and a pleasant place for members to hang out and network. The society organises a programme of public lectures, offers a "safe space" for debating contentious issues, spreads knowledge of the Commonwealth (for example to teachers scrabbling around to find information for a compulsory unit on the national curriculum) and runs youth projects across the Commonwealth - under the rubric of "global citizenship".

In all these ways, the RCS retains certain links with its scholarly origins, and about 15 per cent of its 5,500 members are still academics. It is perhaps significant, however, that the new clubhouse was financed largely by selling the society's archives and extensive library to the University of Cambridge.

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The RAS has followed the opposite route, by moving into cheaper new premises near the British Library precisely so it would not have to sell its collection. It now operates with only two full-time staff.

Alison Ohta, the curator, stresses that they have tried to address concerns that the society had become "a bit elitist, an academic gentlemen's club" - even the fellows' room is often rented out to generate income - but the programme of fortnightly general-interest and more specialist lectures, study days and conferences, backed up by a quarterly journal and some very scholarly publications, is still resolutely highbrow.

While the IMechE's reception area remains pretty old-world, its prominently displayed new vision statement sets out a very different direction, claiming it as "a forward-looking campaigning organisation" committed to "improving the world through engineering". Even bolder is its boast: "Wherever there is an engineering challenge you'll find us."

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Mechanical engineering touches on many areas that are economically important and of wide general interest: the automotive industry, space travel, even medicine (the annual incontinence seminars are surprisingly popular).

But much of IMechE's wider communications strategy focuses on education and three other key themes - transport, energy and the environment - where engineers will be crucial in providing answers to major challenges.

The IMechE press office can suggest media-friendly or telegenic engineers at short notice (something that many member organisations strongly resist). And one of the core goals it shares with many other learned societies is neatly summarised by the director (engineering), Colin Brown: "We are at the interface between the people who know and the people who need to know."

But even today IMechE looks backwards as well as forwards. Its Engineering Heritage Hallmark Scheme awards prizes to "objects, artefacts or locations" that, among other things, are "industrially innovative" and have "made a significant contribution to society and/or mechanical engineering".

Last year, one was given to the Brooklands Museum in Weybridge for its restoration of the last active Vickers Wellington bomber (unearthed in 1985 by a group of people looking for the Loch Ness monster). The ceremony reunited the bomber with some of the surviving RAF crew. This year's winners include a Victorian sewage plant.

On a more contemporary note, in October, IMechE launched its Vision Awards for engineers of the future who demonstrate "talent, leadership skills, motivation and a desire to educate the next generation". The awards are given to an undergraduate, an engineering technician and an apprentice with a Whitworth Scholarship for further study. It can be only a good thing that the first undergraduate winner, Siobhan Kohli-Lynch, is outspokenly eloquent about the need to get more women into engineering.

Radical recent changes at the Royal Geographical Society (RGS) have been introduced to help the society abolish what it describes as "the popularly held but misplaced image of an elite gentleman's club". It, too, has done so by facing both ways - literally in the case of its London home.

Founded in 1830, it has been housed since 1912 in Lowther Lodge, set back from Kensington Gore, opposite Hyde Park. The building was designed by Norman Shaw in the 1870s in Queen Anne style, and looks rather like the courtyard of a country house that has been misplaced in central London. It fits in well with the high Victorian kitsch of the Albert Hall and Albert Memorial nearby, but it could hardly feel less welcoming or democratic.

To meet the challenges of the 21st century, the RGS built a light and friendly modern extension and, in 2004, moved the main entrance around the corner in Exhibition Road. This has enabled it to reach out and attract more of the 28 million people a year who visit the nearby museums.

It provides public access to the largest private geographical collection in the world: a million maps, half a million photographs and a quarter of a million books. Much of this material is "historic", doubtless acquired by colonial administrators and aristocratic adventurers. But exhibitions drawing on them as well as contemporary objects and images, such as the recent one on the Punjab, also help forge links with Britain's ethnic communities.

The RGS still retains a strong scholarly core, facilitating and disseminating research, producing three major journals and hosting the world's second largest annual geography conference. It maintains fortnightly contact with all the heads of geography in British universities.

The society provides resources to teachers whose geographical knowledge is out of date. And it organises 175 lectures a year at its headquarters, in the City of London, across nine regional branches and even in Singapore and Hong Kong.

The director, Rita Gardner, shares her office with the table on which David Livingstone wrote up his African travels. As the official adviser on geography to the Department for Children, Schools and Families, she is committed "to making sure policy-relevant research is heard". Learned societies, she argues, should stand for balance and independence. "They can flourish if they build on their scholarly strengths and can deliver publicly relevant goals."

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Many are indeed flourishing as they negotiate careful paths between past, present and future, via scholarship, lobbying and outreach. But at least one thing is sure: no one can regret the day when only "gentlemen" could become members.