Exactly as the title says, here's a lengthy list of the ones i'm aware of. For the Steam links, see here on how to download them without downloading the game itself (You still need to own the game in the first place, hence why the links are only to F2P titles.) As for the PS3 links, you can just transfer the files onto a standard USB Drive after downloading, then use them anywhere.
- 7 Billion Humans
- Anodyne
- Adventures of Pip
- Anarchy Online (Requires Steam.)
- Bloodrayne: Betrayal
- Boot Hill Heroes
- Canabalt
- Cat Girl Without Salad
- Chicken Wiggle
- Cinders
- Company of Heroes 1 (Scroll down a bit if you somehow can't see it.)
- Datura (Requires a PS3 and a US PSN account.)
- Dear Esther (Original mod, the remake's soundtrack is not free.)
- Divekick (Scroll down.)
- Double Dragon Neon
- Edge
- Escape From Puppy Death Factory
- Free To Play (Technically a documentary about a game, but it still counts. Requires Steam.)
- Gravity Hook
- Gravity Hook HD
- Greed: Black Border (Scroll down.)
- Human Resource Machine
- Impulse
- Joe Dever's Lone Wolf (Requires a PS3 and a US PSN account.)
- Kaleidoscope
- Knytt Underground
- Little Inferno
- Marie's Room (Requires Steam.)
- Mayhem Triple
- Merry Gear Solid 2
- Mighty Milky Way and Mighty Flip Champs
- Mighty Switch Force
- Mighty Switch Force 2
- Missile Master, Episode 1: Invasion
- Momodora II
- Mutant Mudds
- Noitu Love 2 and Legend of Princess (Scroll Down.)
- NyxQuest: Kindred Spirits
- Perfection.
- The Oil Blue
- Portal 2
- Puzzle Dimension
- The Real Texas
- Return All Robots!
- The Sea Will Claim Everything
- Shantae: Risky's Revenge
- Shantae and the Pirate's Curse
- Shooty Skies (Requires Steam.)
- Shovel Knight (Including the expansions "Plague of Shadows" and "Specter of Torment". An arrangement album is also available.)
- Slam Bolt Scrappers
- Soul Fjord
- The Spirit Engine
- The Spirit Engine 2
- SteamBirds
- Street Fighter X Mega Man (See here for a few bonus tracks.)
- Super Crate Box
- Super Street Fighter II Turbo HD Remix
- Supreme League of Patriots
- Trenches
- Torchlight II
- Toto Temple Deluxe
- Ultionus: A Tale of Petty Revenge
- Warlock Bentspine
- World Of Goo
- Xeodrifter
- Zero Gear
- Zombie Panic! Source (Requires Steam.)