Mwave offers the iStarUSA 3U Compact Rackmount microATX Server Chassis, model no. D-313SE-MATX, for $54.99 with free shipping. That's tied with our January mention as the lowest total price we've seen. (It's a current best by $10, outside of the price below.) It features a 15" depth, two external 5.25" drive bays, one external 3.5" drive bay, four internal 3.5" drive bays, front-side USB, power and reset switches, and room for up to four full-height add-on cards.
A close price: Newegg offers this for $49.99 plus $5.99 for shipping.