CryENGINE 3 : free SDK for non-commercial work

The CryENGINE is a professional Game Development system, in which you can fully author interactive content, games, simulations. The Software Developers Kit (SDK) was already free for schools, but now individual students can also freely use the 3D engine.

It is a powerful platform, but it requires fairly up to date hardware and Windows.

I have not had the chance to use it, nor play any of the CryENGINE powered games, but it is one of the more famous ones (apart from the Unreal Engine and the Unity3D engine which both are also freely available under certain limitations).

Info on

(Edit: Feb 2015 > updated the above link)