I will soon be releasing a number of free bitstreams to mine with FPGA's with better ROI's than GPU's, and if you want silent mining you can use the Nexys Video card (XC7A200T FPGA).  Be warned, you can only mine Keccak (Smartcash, Maxcoin) and SHA-224 (Bismuth) profitably, but the card draws minimal power, needs no fan, costs $490, and makes around $2.11 per day at today's prices which is more than many GPU's.