Hrm… Good question! 
Overall, probably the best would be Scarleteen, which has pretty open, sex-positive, and "sex novice" focused content… Aimed primarily at minors, the knowledge is applicable to anyone (though the community elements are not friendly to stalkery adults, obviously):
For more "street knowledge" type education, few things could be better than simply reading a month's worth of craigslist casual encounter ads: http://craigslist.org/cas
I hate linking to Mashable, but Geoff Livingston had some interesting thoughts on the matter in an article last year: http://mashable.com/2010/03/12/s…
deano.com 