I guess this is a morning for soundtracks, too bad this one isn't free like Invincible Tiger's. The Trine official soundtrack is out and and available for purchase. The price? About 12 euros. But you can snag the amazing main theme for free, and we do recommend that.
Composer Ari Pulkkinen has it on his official site, along with some works of other games he did music for - like Super Stardust HD and Shadowgrounds. It looks like Ari has some good taste in co-op games at least! Now we just need the PlayStation Network version to finally be released and all is well with the world.