"Skin" - Rihanna for pop side of R&B. Just love that song with a partner.
Christina Aguilera has some sexy seductive covers on the more blues side of things (e.g. "Nasty Naughty Boy").
For something hip-hop, personally a more playful style of music, Taio Cruz ft. Ludacris, "Break Your Heart".
[Suggestions if you want to rip the panties off (definitely not R&B, couldn't think of one): Lady Gaga - "I like it Rough" (Pop/ Dance, about not wanting to get involved). For rock, Halestorm is awesome, "Innocence" (warning someone that all you want is sex), "Familiar taste of poison" (slow, about being addicted to someone), and "Love Bites" (about doing for you what your GF won't).]
Classical music can also be sexy, I really like "Kismet" by Bond, you really want something with cello. Worth a listen, it is physically stirring.