In my spare time I've been working on a RAID-lookalike system for storing large amounts of data with multiple redundancies - and with significantly lower power consumption and disk spinning time than standard RAID if you only access single large files in a typical session.
The whole thing is implemented as a network block device (nbd), and will be presented (in an early, but at least already partially working state) on LinuxTag 2010 in Berlin.
Note that this is not a direct competitor to a standard RAID solution - in fact, I propose using a RAID 1 for the journal it needs (e.g. use the system disk - you're already using a RAID there, right?). For a comparison table check the project page.
Source will be available soon, I've not decided which git hoster to use yet. I don't think it's reasonable to put this on freedesktop, because is relation to freedesktop to close to nothing. I might change my mind, though .