Amazon has some of the best deals we've seen in a while, with steep discounts on various titles launched earlier this year. Some notables include Mass Effect 3 for $15.99, all the Crysis titles for $14.98, Borderlands + DNF + The Darkness II for $19.99 (or just The Darkness II for $9.99, cheaper than Steam's weekend sale), GTA IV + Max Payne 3 for $29.99, BioShock 1 & 2 + Spec Ops The Line for $19.99, Syndicate for $9.99 and many more. There's not a ton to see elsewhere, though GamersGate has 75% off Supreme Commander and GameFly offers 75% off Napoleon: Total War and various Square Enix titles.

Steam
77 The Darkness II $12.49 (75% off)
70 Age of Empires Online DLC: Celebration Bundle $2.49 (50% off)
81  Vessel $9.99 (33% off)
Lunar Flight $4.99 (50% off)
Containment: The Zombie Puzzler $2.99 (40% off)
Vertex Dispenser $3.39 (66% off -- today only)
War of the Immortals Starter Pack $4.99 (67% off)
War of the Immortals Wander's Pack $14.99 (50% off)
More...

Amazon Digital
86  Mass Effect 3 $15.99 (60% off)
86  Mass Effect 3 Digital Deluxe Version $19.99 (60% off)
86  Crysis Maximum Pack $14.98 (79% off)
83  Borderlands + DNF + The Darkness II $19.99 (80% off)
84 Grand Theft Auto IV + Max Payne 3 $29.99 (67% off)
86  BioShock 1 & 2 + Spec Ops The Line $19.99 (78% off)
81 Kingdoms of Amalur: Reckoning $15.99 (60% off)
77 The Darkness II $9.99 (80% off)
77 Split Second $4.00 (80% off) 
86 The Sims 3 $11.99 (60% off) 
79 Metro 2033 $10.00 (50% off)
73 Syndicate $9.99 (67% off)
80 Divinity II: The Dragon Knight Saga $5.99 (85% off)
80 Need for Speed Ultimate Digital Collection $11.99 (60% off)
68 Saints Row 2 $7.50 (50% off)
89 Dead Space Dual Pack $7.99 (80% off)
79 R.U.S.E. Bundle $7.39 (80% off)
73 Prototype 2 $24.99 (50% off)
71 Red Faction: Armageddon $10.00 (50% off)
X-COM: Collection $3.75 (75% off)
Disney Kids and Family Pack $8.99 (94% off)
Final Fantasy XI: Ultimate Collection $9.99 (50% off)
More...

GameStop
72 Majesty 2 Collection $6.79 (66% off)
67 Dungeon Siege III Bundle $12.49 (50% off) 
69 Warhammer 40k Dawn of War Collection $16.99 (66% off)
More...

GamersGate
82 Supreme Commander Gold Edition $5.00 (75% off)
77 Gray Matter $7.50 (75% off)
85 Runaway 3: A Twist of Fate $5.99 (70% off)
65 Yesterday $14.98 (50% off)
62 Cursed Mountain $4.98 (50% off)
74 Dark Fall: Lost Souls $4.98 (50% off)
Ultimate Crime Thriller Collection $7.49 (75% off)
Ultimate Mystery Collection $4.99 (75% off)
More...

GameFly
76 Men of War $3.75 (75% off)
76 Men of War: Assault Squad GotY $9.99 (75% off)
74  Men of War: Red Tide $6.25 (75% off)
83 Torchlight $5.00 (66% off)
82 Just Cause 2 $4.99 (75% off)
91 NBA 2K12 $5.00 (75% off)
82 Napoleon: Total War $5.00 (75% off)
67 Arcania - Gothic 4 $5.00 (75% off) 
87 Deus Ex: Human Revolution $7.49 (75% off)
71 Quantum Conundrum $3.75 (75% off)
Thief: Deadly Shadows $4.99 (75% off)
Hitman: Codename 47 $2.49 (75% off)
Hitman 2: Silent Assassin $2.49 (75% off)
Hitman: Contracts $2.49 (75% off)
More...

Green Man Gaming
20% off any title via code "DERHE-RRDER-RINGE"

GOG
50% off strategy titles