Bandwagon, the little OS X application that backs up your iTunes media online, will be relaunching this evening as a DIY version. Just give it your Amazon S3 account info and you're good to go. I've been beta testing it for about a month now and am quite pleased with how it works.
I say "relaunch" because Bandwagon initially came out in late February with the promise of unlimited storage for users. They quickly learned they wouldn't be able to satisfy peoples' insatiable storage needs and relaunched with this Amazon S3 capable solution. My buddy Dan at UNEASYsilence has a top-notch video review going through the features of Bandwagon; definitely worth checking out if you're considering hopping on the Bandwagon (bad pun, I'm sorry).
Dan says he was able to backup his over 300GB iTunes collection using Bandwagon - pretty impressive. My iTunes music is a lightweight at under 10GB, and that still took about 2 days to upload.
Speaking of which, iTunes 7.2 was released yesterday, adding support for iTunes Plus in the iTunes Store (DRM-free music from EMI) as well as iTunes U.