For mATX boards, Addtronics makes a nice small case (F2901) that is about the size of those book-sized PC. It will take a normal mATX board but the add-on cards need to be "short" add-in cards. By short, I mean the metal bracket on the end of the card is not the normal height.
For inexpensive cases, I find the InWins are good and I never had a problem with their powersupplies. I also like the Palo Alto cases but they tend to be $$$$. Just stay away from those $20 cases.