Steam's long-awaited summer sale has finally commenced, with over 5,000 games currently discounted. Naturally, we can't include that many titles here, so we've just added today's hottest promos (some of them will expire in mere hours, so act quick). Although Steam will likely hog your attention until July 22, other distributors have noteworthy deals, such as Amazon's $15 THQ Action Pack and Civilization IV + V for $11.99. GameFly has big savings on BioWare games, GamersGate offers L.A. Noire for $9.98 and Green Man Gaming has hundreds of discounts as part of a seasonal sale similar to Steam's.

Steam
84 Max Payne 3 $29.99 (50% off)
82 Tribes Ascend Starter Pack $4.99 (75% off)
72 Indie Bundle II $9.99 (75% off)
76 From Dust $3.74 (75% off)
83 Sonic Generations $10.19 (66% off)
75 Warhammer 40,000: Space Marine $7.49 (75% off)
69 Payday: The Heist $4.99
83 Anno 2070 $24.99 (50% off)
82 The Binding of Isaac $1.24 (75% off)
83 Worms: Reloaded $4.99 (75% off)
88 Super Street Fight IV: Arcade Edition $9.99 (75% off)
Ghost Recon: Advanced Warfighter 2 $2.49 (75% off)
Assorted Bundles
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Amazon Digital
66 Sniper Elite V2 $14.99 (70% off)
83 Borderlands GotY $7.49 (75% off)
82 THQ Action Pack $14.99 (84% off)
86 BioShock Dual Pack $7.49 (81% off)
73 Spec Ops: The Line $24.99 (50% off)
89 Dead Space 2 $4.99 (75% off)
64 Binary Domain $9.99 (75% off)
87 Deus Ex: Human Revolution $6.99 (77% off)
90 FIFA Manager 12 $9.99 (50% off)
71 Alice: Madness Returns $4.99 (75% off)
86 Need for Speed: Hot Pursuit $4.99 (75% off)
87 Civilization IV + V $11.99 (80% off)
68 Command & Conquer 4: Tiberian Twilight $4.99 (75% off)
77 The Darkness II $12.49 (75% off)
81 Bulletstorm $4.99 (75% off)
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GameStop
87 Burnout Paradise: Ultimate Box $4.99 (75% off)
74 Dead Island $14.99 (50% off)
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GamersGate
87 L.A. Noire $9.98 (80% off)
88  GTA: Episodes from Liberty City $14.98 (50% off)
GTA IV $10.00 (50% off) 
GTA: San Andreas $7.48 (50% off)
Sword of the Stars Complete Collection $4.99 (75% off)
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GameFly
62 Gotham City Imposters $3.75 (75% off)
87 Mass Effect 3 $35.99 (40% off)
93 Mass Effect 2 $4.99 (75% off)
90 Mass Effect $4.99 (75% off)
90 Dragon Age: Origins $4.99 (75% off)
90 Dragon Age: Origins Ultimate Edition $7.49 (75% off)
79 Dragon Age II $4.99 (75% off)
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Green Man Gaming
83 Saints Row: The Third $17.97 (60% off)
79 Metro 2033 $4.98 (75% off)
82 Darksiders $4.98 (75% off)
Warhammer 40,000: Dawn of War II - Retribution $11.99 (60% off)
Company of Heroes $2.48 (75% off)
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GOG
50% off Ubisoft strategy titles