Oh, 4chan, the things you have me read...

[sakura_no_miko]

http://www.hellodamage.com/tdr/archive/sex/sounds.htm
A dictionary of Japanese sex FX...mostly ones that don'r pertain to yaoi, unfortuantely.

Oh, and the non-perverted ones:
http://www.oop-ack.com/manga/soundfx.html