CNFPS (Creatively Named First Person Shooter) is a new project that aims to be a technically and visually impressive FPS which utilizes a client/server model for enabling multiplayer.
Currently there are no official releases, only snapshots generated automatically from SVN. These snapshots should be relatively stable, but I don't think there's enough there to justify a formal release yet.
32-bit and 64-bit Linux are the only platforms I have real hardware dedicated to, and thus can easily build for. The Windows binary is cross-compiled using MinGW. Other platforms will probably work too, provided they have a working compiler along with OpenGL and SDL installs, but are currently untested.