Been looking at this today if you have an old box and some spare drives sitting around. unRAID server
http://lime-technology.com/Advantage of "not" using traditional raid but still being able to pool drives into shares.
Uses 1 (largest) drive as a parity drive (the whole drive is a parity drive) and then pooling the other drives.
Advantage is if you want to upgrade one of your drives, or it crashes you can just replace it and it will rebuild that drive. Does it for both the parity drive or any of your pool drives.
Simple interface via web, runs headless, boots off a usb drive, spins down drives and when accessed will only spin up the drive which has the data you need.
Low end PC hardware requirements
Best thing is it is free for up to 3 drives and low cost licence after that.
Might have to have a play with it tonight.