Besides some of those already listed (ie Stephen Lynch), I'm a fan of Bloodhound Gang.
Possibly their best known song, Bad Touch (aka Discovery Channel). Warning for lots of sexual innuendo.
Uhn Tiss is my favorite song though. Warning: Honestly, it probably doesn't even need a warning, but there is implied sexual contact. It's much less risque than a Mass Effect sex scene and is the punchline of a joke they take the whole video to set up.
Their other songs I enjoy:
Lift your Head Up High(And Blow Your Brains Out)
I Hope You Die
No Hard Feelings
Right Turn Kyle (These last four are awesome anger/hate songs, especially No Hard Feelings for a break up)
Three Point One Four
I'm The Least You Could Do
I Wish I Were Queer So I Could Get Chicks
Mope
The Ballad of Chasey Lain
A Lap Dance Is So Much Better When the Stripper Is Crying