Personally if I want a mega extreme cheap case, I just go to the local computer show (
www.marketpro.com has shows over a good section of the country, and if you print out the web site coupon or the email telling you when the show is you can get in for I think $5 or $6). They have cases for like $20 with 300 watt power supplies, total with the price of admission (assuming you don't buy anything else) thats about $25 bucks out the door with a extreme cheap case. I picked up one for a computer I was building for my grandma for about $30 out the door that even has front USB ports, and mobo tray, rounded edges, etc all the normal goodies. I was surprised at how decent the case was for that cheap. I also picked up case fans for like $3 each, floppy drive for $9 out the door, etc (this was all new parts). With the small components, you'd be amazed at how much you save going to one of those. Now with the major components, you are probably better off hitting newegg for the CPU, and mobo. Now if you want something good for a bit more, I suggest something like the ever cases at new egg, I think they are like $40 shipped without power supply and a few bucks more if you get it with 300 Watter.
Just a few suggestions from my experiance, yes it is more trouble to have to actually exit the house and drive somewhere on a weekend, but if your main concern is saving money, that can do it

Its a great place to pick up adapters and misc parts too, all the stuff you wouldn't normally want to order by itself since the shipping would more than double the price on those kinda small inexpensive items.