If you are interested in music related APIs, my company (http://www.audiogalaxy.com) has a draft API that lets you browse and play your music collection remotely. We support mp3, aac, flac, wma, vorbis, and get your playlists out of iTunes.

We haven't publicized the API quite yet, but we would love get feedback from anybody who might be interested in it. Send me an email if you are: twk@audiogalaxy.com