Assuming you aren't knee deep in Crysis 2, there are some pretty enticing deals this weekend. In addition to knocking 75% off Lead and Gold, Steam is letting users play the game for free this weekend. The service has also reduced The Witcher by 50% in anticipation of its upcoming sequel, and Black Ops is 25% cheaper than launch. Meanwhile, Impulse has cut half off Dragon Age: Origins Ultimate Edition, GamersGate is selling Battlefield: Bad Company 2 for $10, and Direct2Drive offers 20% off its entire catalog via coupon code "MARCHMADNESS".
Steam
Lead and Gold: Games of the Wild West $2.50 and free weekend (75% off)
The Witcher: Enhanced Edition Director's Cut $9.99 (50% off)
Neverwinter Nights 2 Platinum $9.99 (50% off)
F1 2010 $19.99 (50% off)
Call of Duty: Black Ops $44.99 (25% off)
Hoard $7.49 25% off
Dreamcast Collection $14.99 (50% off)
Arcadia $2.49 (50% off)
Ghostbusters: The Video Game $9.99 (50% off)
Sacred 2: Fallen Angel $9.99 (50% off)
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Impulse
Dragon Age: Origins Ultimate Edition $24.97 (50% off)
Fate of the World $7.49 (25% off)
Full Spectrum Warrior Complete Pack $9.99 (50% off)
Astral Masters $9.97 (50% off)
Jets'n'Guns Gold $10.18 (66% off)
The Stalin Subway and The Stalin Subway: Red Veil $7.49 each (50% off)
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GamersGate
Battlefield: Bad Company 2 $9.98 (50% off)
R.U.S.E.: The Art of Deception $14.98 (50% off)
Call of Juarez 2: Bound in Blood $9.98 (50% off)
King's Bounty: Armored Princess $7.98 (60% off)
Football Manager 2011 $19.98 (50% off)
Men of War Red Tide $7.98 (60% off)
Cities XL Standard Edition $9.98 (50% off)
The Oddboxx $12.48 (50% off)
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Direct2Drive
20% off all games via coupon code "MARCHMADNESS" (doesn't stack with other deals)
75% off Direct2Drive's top driving games
Call of Duty: Black Ops $44.95 (25% off)
Games for Windows
Dirt 2 $19.99 (50% off)
Good Old Games
40-60% off Enlight games
EAStore
FIFA Soccer 11 $20.00 (50% off)
FIFA Manager 11 $19.98 (50% off)