There is no OST cd out. There have however been quite some requests by fans, and some of the Larians themselves would like to see it happen as well. But it all depends on Kirill, composer and man of mystery (read: where the hell is he hiding now?!)

The following links might interest you though:

Brainbox' Divine Divinity Music Extractor - Program that extracts all the music into .ogg files (which you can convert to mp3, of you wish)
Some tracks at the website
Christmas present from the Larians: 11 mp3 tracks from the game

Mr Kej, Second Member of the Guild of Off-Topic Posters *** Visit Aviorn's Inn, my Divine Divinity fansite ***