Here come the ABCs CD/DVD is pretty fun. I was always a casual TMBGs fan, but never actually listened to a whole album, or anything cliche like that... My kids dig the ABCs, and I've heard/watched that one about 20 times.
But we also borrowed their "Here Comes Science" from the library. I was frankly pretty turned off by how hard they were pushing atheism on my 4 and 5 year olds... here comes science, indeed.