Any intel 915 chipset is decent. The more expensive 925 is also great if you can afford it. The chipset in part of the mobo, so just look for the chipset in a mobo. Be sure to make sure the mobo socket matches that of the mobo you bought. For the current intel prescott's, the socket is 775
Your case takes ATX form factor mobo's so make sure any mobo you buy is ATX compatible.
I didn't buy any motherboard yet.