I just started to play with FreeNAS.
If you have an old PC laying around, it works fairly well.

My advice though, forget software RAID. Too unstable. 
I had 3 80Gig drives set up with software RAID5 and we lost 
power Monday night (yeah I know, I should have had it on a 
UPS). RAID go bye-bye! :-) A quick Google of the situation
showed that it just wasn't worth my time to try and recover
the RAID or data since the data was backed up elsewhere.

So I re-allocated the drives as just 3 seperate drives with 1
share per drive. No redundancy, but I'm not worried about
that (it would have been nice, but not critical).

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Todd Young