RedOrbit posted an interesting article about a German scientific experiment in reducing tinnitus using music.
According to the article, the researchers took music that the patients like and "stripp[ed] out the sound frequencies that matched the individual's tinnitus frequency." The patients then listened to this music for a year, and "reported a distinct decrease in the loudness of the ringing."
Wikipedia has an interesting list of the causes of subjective tinnitus. I can see this being a pretty neat new therapy for people who suffer from the problem.