Amazon has the Rosewill SCM-01 Micro ATX Mini Tower Computer Case for $20 with free shipping on $25+. Newegg has it for the same price (10/12 only).

Supports Micro-ATX and Mini-ITX M/B, has 4 expansion slots, three internal 2.5", three 3.5" internal drive bays, and one external 5.25" drive bay.