Jimmy Buffet (shut up, don't laugh, i'm a fla girl) does a remake of Southern Cross,by Crosby Stills & Nash. I never really cared much for the original but i love Jimmys cover of it. He owns that song.
I also like UB40's Many Rivers To cross orginally by Jimmy Cliff & their cover of Red,Red, Wine orginally by Niel Diamond, i think.
But my very favorite would be Phish's cover of Snoops Gin & Juice as dark_angel177 already mentioned. I listen to that song often. I didnt even know what most of the words were intill Phish covered it.
i know i'm missing tons of songs but that's all i can think of right now.