A few more:
Povray (freeware) - A powerful raytracer with lots and lots of features, the only problem is that it doesn't have any sort of GUI so you have to design everything in a C++-like scripting language.
www.povray.org
Moray (shareware, $80?) - A graphical "front-end" for Povray which supports most of Povray's features. Powerful but has a steep learning curve (on the other hand it's no Blender!) Trial period is not enforced so you can use it as long as you like, and the shareware Version is not missing any features. An animation plugin is available.
www.stmuc.com/~moray
Art of Illusion (freeware) - A Java-based raytracer and modeller that has some interesting features, such as "procedural textures" (defined by mathematical function that can vary over space and time). Includes built-in animation support. However these procedural textures are rather confusing if you don't understand functions, and the program, being Java-based, does not support the standard "double-click on a file, launch the application" feature.
www.artofillusion.org
Blender (freeware) - Formerly a major commercial raytracer/modeller, Blender was recently released as freeware. I downloaded it and couldn't make heads or tails of it - anyone have a clue? (Can't remember the URL but try looking it up on Google)