Nerve.com: part of the "smart-sex" movement; an online magazine that publishes "cuntsure (and cocksure) prose and fiction as well striking photographs of naked people that capture more than their flesh."
Bear community: homosexual subculture encompassing men with stocky builds, facial hair and hyper-masculine demeanors.
Philly cubs: a Penn-affiliated social organization for 18-25 year old "bears, cubs, chubs, Ursulas, transbears, admirers & friends." Not for the Berensteins.
Twinks: slang for the opposite of a bear: an attractive, effeminate, younger gay man. Can have pejorative connotations.
Yiff: sex between one furry character persona and another in cyberspace. Check out the profusion of yiffy art if you need a visual.
Sex-positive: an attitude or social movement advocating sexual activity and experimentation as healthy and fundamental.
BDSM: a grouping of related sexual practices: Bondage, Discipline, Submission & Masochism. Aimed at challenging bounds of conventional sexuality.
Vanilla: used as an adjective ("vanilla sex") to describe conventional sexual behavior.
Polyamory: a lifestyle open to having more than one intimate, emotionally-attached, relationship at a time. Not to be confused with passe practices of swinging and polygamy.
Goatse: Google it.