I'd say 90% of my friends are people I met on Craigslist, either buying stuff from them, selling stuff to them, bartering (usually plants), and the majority, as David mentioned, under Activity Partners (women to ride bikes with). I think that Craigslist has a different vibe in each city, but in my city, it's a fantastic grass-roots crowd.

I even have a Craigslist tshirt...