I like Pop. It makes me exited and think faster. I think is goes along well with Blitz.

I enjoy rock music for long games (1+ hour) Also I believe a calm music can really help one.

naturally:

The way I'm playing at the moment, early Leonard Cohen or Faure's Requiem

The BEST music while playing chess?  None.

Do you think that you will play better if you focus 100% on your chess game, or if you focus mostly on your chess game, and a little bit on the music you are listening to?  Music competes for your attention while you are playing chess, so it cannot help your game.  But if you enjoy playing chess more while listening to music, then by all means do so, since it is all about enjoyment for most of us.

Without a doubt Chaka Khan

Snoop Doggy Dogg

Classical music, preferrably during the Baroque era.

Music messes me up. I can't listen to music at all when i play chess. I wish I could, I would, but I can't.

I don't know if it matters what sort of music...anything you like. I think the point is to block out small distractions, e.g. ticking clocks, people coughing, etc.

I second The Smiths

U2!

Henry Cow, if I'm playing Henry Cao.

Then for speed chess, there's always this:

http://www.youtube.com/watch?v=APl9fRFmdC0

Arcade Fire - Deep Blue

http://www.youtube.com/watch?v=l_-pm6DFmrA

Jazz. Miles Davis.

 http://www.youtube.com/watch?v=rpzCiyt_uHM

I always listen to music while playing bullet (but only bullet - music doesn't work well for me on other time formats), Nirvana, White Zombie, Nine Inch Nails and Sisters of Mercy! 

The Funeral march by Berlioz when I am losing, and Happy Days Are Here Again when I win.

I play or sometimes watch(!) anime in the background... xD yeah, it really helps me concentrate, yep.

Try One Inch Punch - Pretty Piece of Flesh while playing bullet. Works like charm.