If you have a CompUSA nearby, check and see if they have the Antec Aria case. It's clearanced to like $59.99, comes with PS and fan. I've had mine sitting in the box for a while with the intentions of making a living room HT/emulation PC, but haven't broken down and bought the parts. Comes with fan, 300W PS, built in media card reader, etc. Here's the link to Antec's product page:
http://www.antec.com/us/productDetails.php?ProdID=15130
I've been thinking about throwing in an old Intel 478 socket board into it, but it doesn't have an AGP slot. From what I've seen, building a 775 socket would probably be cheaper with all the deals that float around. Personally, from the SFF case prices that I've seen... they seem to be a bit overpriced at times.
Strell, I agree on the case building thing.. I've seen some really cool case-making/molding walkthroughs out there, but there's no way in hell I'd go to that much trouble. Plus, we all remember the infamous TechTV NES PC thing.. if I gave that a shot, I'd probably end up with a grey, red, and black molten pile.
Oh yeah.. one more thing. I wish I had a link, but I've seen a custom PC company out there that uses wooden cases. Personally, I think it'd be cool to have an oak/cherry PC case.. but something about mixing electrical components and wood is kinda wonky and risky. Still... pretty classy looking nonetheless.