Interesting. Marianna over at Crowe's Nest writes about writing sex scenes in YA novels. She dissects a number of scenes in novels such as Melvin Burgess's Doing It and Daria Snadowsky's Anatomy of a Boyfriend, among others, and shows how the best ones aren't there for titillation, but reveal what's going on for the characters at the time. (Which is basically Rule of Good Writing Number One.)
I have to say, the best sex scenes I've ever read were in Pop! by Aury Wallington. They weren't Teh Sex-ay by a long shot, but they were incredibly honest, even a little clinical (which worked for the book and the character). I kinda loved it.
What's the most memorable sex scene you've ever read in a YA novel?
Thanks to Lisa Chellman for the link!