The charities that have followed the WDM's lead include Macmillan Cancer Support, Save the Children, the NSPCC and Amnesty.
But the list of online communities is bewildering: besides Second Life, it includes Facebook, del.icio.us, Wayn, MySpace, Bebo, Habbo Hotel and Dubit. So where should fundraisers start?
1. Where to fundraise?
Charities can set up profiles on Facebook or MySpace and invite people to join them. Cancer Research UK's MySpace profile has nearly 8,000 friends.
"MySpace doesn't have an official partnership with an organisation such as fundraising website JustGiving, but charities can build their own widgets to receive donations via the site," says Chris McCafferty, head of communications at MySpace.
Facebook lets fundraisers accept international donations and reclaim tax from UK taxpayers through JustGiving. Other interactive forums include bbc.co.uk or Guardian Unlimited. Alastair Irons, executive creative director of direct marketing agency TW CAT, says: "The whole of bbc.co.uk is open to public comment. There are plenty of opportunities for charities." For example, a cancer charity could respond to a news story about sun cream and direct readers to information and a donations page. Irons adds: "There is a huge number of interactive forums with powerful ways to build your profile and talk to supporters."
2. Build a network
Charities could load campaign videos onto MySpace's video player for users to grab and share, or they could design badges or banners for users to post on their pages.
"Encourage friends to list your charity among their friends and send bulletins to their friends about your organisation," says McCafferty. "Find active groups that are relevant to your organisation and participate in their forums to get the word out. If you have relationships with bands, politicians or celebrities with supporter communities on MySpace, ask them to post your badge or send out a bulletin."
Information should be easily accessible. Instead of asking supporters to click for newsletters, embed information into profiles. "Let supporters link to employees, volunteers and beneficiaries who also have online profiles so they can interact," adds McCafferty.
3. Convert supporters into donors
"Don't forget to drive supporters to your donations page," says Irons. "Online communities should end up being directed to bespoke fundraising microsites, charity donation pages or JustGiving sites. Donation sites must be able to accept all methods of payment, so get involved with online payment service providers WorldPay and PayPal."
Fundraisers can also prospect online, by getting people to sign up to receive information from charities on volunteering, campaigning or donating. Prospects could later be converted into donors through channels such as direct marketing or telephone calls.
4. Manage networks
Charities could appoint cyber-fundraisers to promote causes online, suggests Irons. "You might have someone building awareness on Bebo," he says. "If so, they need to have a presence on every forum that is discussing the relevant issues and drive visitors to donate."
5. Be a pioneer
"If you're not on it by now, Facebook is already getting away from you," says Irons. He says charities should consider investing up to 10 per cent of their marketing budgets on researching pioneering approaches.
However, Nicolas Roope, founder partner of advertising agency Poke, is cautious. He says: "I would dissuade people from trying to be ahead of the curve. There are very scant returns."
He points to media and advertising blog PSFK.com, which says only 10 per cent of Second Life users are active. "Until recently," Roope says, "people were getting a reasonable amount of PR out of Second Life, but now those stories have been reported so much they aren't something amazing. As a result, there's no value.
"When things are cutting-edge they tend to be very young and fragile and have few users. The focus should be on concept-rich campaigns delivered in an appropriate manner."