MTV which seems to play no music at all now
MTV2 which plays modern rock
MTV Base which is a hip-hop one I think
MTV Dance which is dance, duh
VH1 which has pretty much everything
VH2 which has modern rock
VH1 Classic which has classic rock
TMF which has mostly pop
The Box which has mostly pop
Kiss which has mostly R&B
Smash Hits which has mostly pop
Magic which has mostly 80s stuff and movie songs
Q which has a good mix of everything
Kerrang which has mostly hard rock
The Hits which has mostly pop
Classic FM which has classical music, duh

There's a few more too that I can't remember. Personally I only ever watch VH1 and VH1 Classic.