Hrm… Good question!
(Probably not the Virgin America website… Photo Courtesy of http://www.fotopedia.com/items/f…)
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 http://mashable.com/2010/03/12/s…had some interesting thoughts on the matter in an article last year: