I just recently came across this site with a new distributed filesystem called MogileFS. Since I read about the Google File System a while back I've been wanting to have something similar for my personal digital archive.
I tend to bump into older hardware quite often, and I want the possibility to use the storage on these machines until it fails. And when the hardware eventually fails I'll just throw it away because of the built-in redundancy of the system. If I notice my replication count is getting low or my disks are starting to fill up, just buy some new disks and place them in any of the existing nodes. When I'm out of physical space on any of the nodes it's about time to actually buy some new nodes or switch the smaller hard-drives with larger ones.
I will look into how MogileFS works during the next weeks and report back about my findings.
Let's hope it's stable and useful for my needs.