Drobo!

Picked up a Drobo recently due to a complete fail with a macally firewire enclosure. (it would keep going to sleep and not coming back on my mac mini at home)  Seems to be working well, setup was easy (shove drives in) and it pretty much works.  Its slow.  30 MB/sec writes is all I've seen.  Dunno about reads, haven't tested yet.  Get a more expensive drobo if you need high peformance, mine is more of a place to stick huge amounts of data I don't need very quickly.

Note: I would still back up any data on the drobo to another disk -- raid is not a backup.