I’ll vote for Annette Bening in The Grifters. The scene where she offers herself for a motel room, “the Intercourse Commerce Commission” scene, is, well, maybe Warren can give us some input here.
Yes. That’s pretty damned hot. 
That first sex scene between Dennis Quaid and Ellen Barkin in The Big Easy will always be one of my favorites.
The sense of anticipation building up between George Clooney and Jennifer Lopez in Out of Sight is good. So is the complete abandon of the scene between Pierce Brosnan and Rene Russo in The Thomas Crown Affair. And yeah, the one between Reese Witherspoon and Ryan Phillippe in Cruel Intentions is also pretty hot. I think it has to do with how they’re kissing.
Y Tu Mama Tambien was just . . . in a class by itself. The sex scenes were great because they were so non-Hollywood.
This thread has reminded me . . . I don’t see nearly as many sexy movies as I once did. sigh
No one has mentioned the train scene from Risky Business.
Hottest Sex scene in a non-porno film… Joan Severance in Payback (not the Mel Gibson movie) ranks in top 5. She was a former Fashion model and starred in Wiseguys in the late 80’s.
The first sex scene in the diner is HOT and she is HOT.
Another vote for “Body Heat.” Steamy in every sense of the word!
Original Sin: Angelina Jolie and Antonio Banderas…rowr!!! yum!!
Does it involve zombies?
It likely says something about my tastes, but the stair scene between Vigo Mortensen and Maria Bello in ‘A History of Violence’ stands out for me.
Yeah.
This is what I came in to post exept for me it’s mmmmm Dennis Quaid.
Zombie sex is messy.
But you can say “I fucked her brains out!” and really mean it.
Tie Me Up, Tie me Down.
Mr. Banderas has taken a long, slow fall in the sexy dept. for me since then… but ooooh he was hot in that movie. And yes, I think there was a sex scene. 
Wow, yeah, that made a BIG impression on me at the time.
The Lover, about a young French girl and her older Chinese lover, has some very steamy near-porn scenes. The actress had just turned 18 when filming started, IIRC. Definitely worth a look.
I haven’t seen these… in the heat of passion, do either of them bite Ralph’s nose off?
The part that continues to bother me in the lovemaking scene in ENEMY AT THE GATES, where they’re making love in the siege of Stalingrad, is that it’s pretty explicitly stated that no one in the city has bathed for weeks and weeks. So Jude Law is slammin’ it to Rachel Weisz and all I think is: they both stink!
The cheerleader scene was crazy sexy, but the stairs squicked me right out.
Does the love scene in **Zack and Miri **count as not porn? 
I thought Rachel was acting like she was being stabbed, not in a good way.
In The Lady Eve (1941, Preston Sturgess, dir.), where Barbara Stanwyick gives a contented sigh of released orgasm while seducing Henry Fonda. Play it in slo-mo…
+1 on this. That was hot!