I've been considering setting up FlexRaid -
http://www.flexraid.com/
It's quite interesting, letting you use drives that already have data on them, any size drives, and can even do network shares.
It's "snapshot" raid though, not "live", which suits me just fine for my home environment. I'm just sick of losing all my data when I lose a drive, and it's only a matter of time before more go.
What's LVM like vs ZFS? It seems like most home file servers are run with ZFS these days