Mostly music that doesn't have (much) lyrics. Specifically, some Infected Mushroom, Skazi, general psytrance radios on the web. Also some Moby, Fatboy Slim... But the best is definitely psytrance. Good psy music makes conducts your thoughts. You alsa have to know what to chose.

Gosh yes. Infected Mushroom - increasing my productivity since 2003. Their music is interesting enough that I still haven't tired of it yet.