A while back Amazon released their S3 service to provide unlimited, reasonably priced, on demand web services based storage space. At $0.15 per GB space used and $0.20 per GB transferred (both per month) it’s rather a good deal.
JungleDisk claims to provide a DAV interface to an S3 account for Windows, Linux and Mac OS X. I’m contemplating giving it a go, just to see what it’s like. It would certainly make a nice off-site backup solution, if it isn’t too expensive. I’m pretty sure that it’s cheaper than co-location, although a little bit limited in scope (relatively speaking).