RAID Parity Applications For Cheap Media?

yamgirl asks: "I've been reading up on RAID strategies for protecting against hard disk failure, particularly those RAID levels that involve recording parity on one disk to duplicate data on multiple other drives, and I've been thinking that this would also be wonderfully useful in making backups to CDROM, or even floppies. Many's the time when I've had a bagful of floppies with me, trying to install something, and found that one floppy out of the batch had crapped out, rendering the rest useless until I went home and got a new copy. If I could make a RAID-style parity disk whenever I needed to make multiple-volume disk sets, I'd only have to carry around three extra disks (one blank to write a new copy on to in case of emergency, and one disk to keep the recovery software on - but the latter two I'd just need one each of for any number of separate sets of parity disks and multi-volume sets of media.) as very effective insurance against crappy disks. Much cheaper in time and effort and disks than making entire extra copies of multi-volume sets, or for that matter of needing to go off site to track down a new copy. ANYHOW, my question is, has anyone ever seen or written any software to do this, to generate parity disks and to recover lost data with them? (And is it free? =)"