Ok,
I don't have much info here so I hope someone can help me out. My coworker was watching a late night talk show, either Leno or Letterman (she doesn't remember which) where there was a rap act that rap to violins. (she thinks violins not 100% sure) it aired sometime in the last 30 days. I tried to do a google search but yeah, that didn't quite work.
I'm looking for the name to band/act thanks

Flight of the Conchords?

Not violins, but folk rap with guitars.

They were on the Late Late Show last night; it was hilarious.

I think I know what you're talking about. IIRC there were two guys who don't rap, but play the violin along to a backing hip hop track.

They were from Showtime At the Apollo.

However, there's also some curly haired chick that plays for Kanye "George Bush don't care about black rappers who destroy classic R&B songs by speeding them up for his songs" West. Here's her link.

Miri Ben-Ari's album "The Hip Hop Violinist" comes out on Tuesday (or available now through um, other means). It's pretty good - lots of guest stars (obviously). In the past she has toured with Jay-Z and Kanye, she did a lot of stuff on Ye's College Dropout, including Jesus Walks, I believe.