I had a problem: I wanted to play my music and podcasts on my ipod from my laptop at work. Installs are locked down so I couldnt install itunes, and I couldnt connect to the music store anyway -- its blocked. Sharepod took care of that with a zero-install fully functional player. However I wanted to listen to my itms downloads which wasnt supported, so I found jhymn. Its very cool -- it will march through your library and unlock all the itms downloads with mp3s, m4a, whatever you want. It even replaces them all in your playlists. Theres an OSX and XP version you can download, and its an open source tool written in java.
http://hymn-project.org/jhymndoc/
