New in Alien Arena 2011 (v7.51) is a rewrite of the BSP surface rendering to yield performance increases, a complete rewrite of the OpenGL vertex buffer object (VBO) code, and a complete rewrite to the post-process effects. There's also improvements to shadow mapping for dynamic shadows, graphical updates and bug-fixes, new and revamped levels, and support for downloading of IQM meshes.
Read more and download from the Alien Arena web-site. There's also a change-log. Alien Arena 2011 was introduced last December.