Vaginal orgasms are not always possible for all women, but for some, the outer third of their vagina is very sensitive, and when stimulated during intercourse or other forms of vaginal penetration, can cause an orgasm. The Grafenberg Spot, or G-Spot, is another matter. We're not actually sure if it exists or not, but it seems to be the consensus that if it does exist, not everyone has one.
I always called it the Steve Guttenberg spot, but anyway.
Also, how to get your roommate to stop "sexiling" you.
That ought to kill their mood.