Sears has the Craftsman 52154 3-Piece Screw-Out Damaged Screw Remover Set for $10 - 15% off in cart =
$8 with free in-store pickup or $7 shipping. Removes damaged Phillips, slotted, hex, Torx or square screws with any variable speed reversible drill or 1/4 in. hex driver.
GearWrench 8 pc. Stubby Wrench Set SAE, 44033 (also Metric, 44034) for $30 w/ free in-store pickup or $5 shipping to home
I was given two of these....I have broken one and have had mixed results. Save your money.
^ Never had a problem with mine, while they don't get ALL screws out they're still worth a shot before you resort to more drastic measures.