Currently described in the US as "the next eBay" (not least because one of the backers is the eBay founder, Pierre Omidyar), meetup is a website that organises local gatherings for people of similar mindsets or interests. Quit-smoking groups, Harry Potter fans, work-from-home mums, people who like knitting - the site helps them get together in restaurants, shops and other meeting places, which effectively fund the thing.
It's like Friends Reunited, except you're guaranteed to have something to say to the people you meet here. Although it's not been going long, indications from the US are that this is going to be huge. All human life is here.
The site: meetup.com
The proposition: A free service that organises local gatherings about
The people: More than 2,500 interest groups are already registered
The pedigree: Founded by Scott Heiferman (of iTraffic fame), backed by
Pierre "eBay" Omidyar