Unity Technologies has added Linux publishing support recently to their popular Unity3D game engine.
With the latest Unity 4.0, developers who wish to provide a Linux version of their game can easily compile source code with the built-in export option and make binaries for Linux platform. Two Unity games, Rochard and Cubemen have already been released for Linux.
If you want to know more about how Linux publishing feature works, check out a presentation by Na’Tosha & Levi Bard from Unity Linux team. In the video John Pugh from Canonical also talks about publishing Unity games to Ubuntu Software Center.