Two new interesting releases:
- Unpacking: As Kotaku said, it contains about 14000 sounds of moving objects... a great library that may be useful.
- A Hat in Time: The very first release on Steam. It does not support mods nor expansions, but it can be run without Steam (without patching the game). So, if you want to run this game on Linux or on computers that don't have Steam installed, this is the version to download.

I know you can play older versions and prototypes of Shadow Warrior with the free version of Shadow Warrior on Steam, I'm not sure that counts in direct relation to this thread though