The O.C.
1. The Girlfriend, Episode 1.6
Caleb’s girlfriend, Gabrielle, seduces Ryan–but the fun ends when Marissa walks in on them.
2. The End of Innocence, 3.3
Ryan and Marissa have sex. (Ignore the fact that Jimmy is being beat-up at the same time). This also ranked on my favorite romantic scenes list.
3. All Marissa/Volchok Kissing Scenes, Season 3
They did it, and they did it HOT!
4.The Summer Bummer, 4.6
Ryan fantasizes about Taylor.
Come back tomorrow for more sexy scenes!
TeenDramaWhore 
Just found this video of The O.C.’s hottest moments put together: http://www.youtube.com/watch?v=m7zAsYqF3Jo