QUOTE (Whitey @ Sep 25 2009, 03:34 AM)

Suicidal Tendencies may suit what your looking for but it isn't really similar to Beastie Boys. It's a hard thing to find

Whitey! You red devil! ST are good. "Institutionalized" being my favorite song.
But yeah it really is hard to find similar artists to the Beastie Boys, quite unique in their own little niche. I might sound like a tool for recommending this, but the band G. Love and Special Sauce have a similar rap/rock/rnb mix. Their second album is quite good, as well as their debut. (And of course their hit single Milk and Cereal)
A rap group called, The Five Fingers of Funk, have a wicked sound of hip hop mixed with a James Brown backing band.
Although what are you looking for specifically, I can't quite seem to put my finger on it. Just rap? Or something else?