While I normally only discus my own projects on this blog, after all it is the Blazing Games Development blog, today I am going to make a bit of an exception and point you to another project that while I am not involved in is one which I will be keeping an eye on. This project is none other than the Apricot project (http://apricot.blender.org/). This is an open source project that is attempting to develop a commercial quality game using just open source tools. In particular, they will be using Blender and the Crystal Space game engine.
Blender is a 3D modeling/animation program that is quite powerful if you can get past the atrocious user interface. That may not be a fair comment since it has been a while since I played with it so things may have gotten better. I just installed it on my Ubuntu machine though doubt I will have a chance to play around with it any time soon. There are also windows and OSX versions available. Still, if you want to create 3D movies, Blender is certainly more than powerful enough and considering it's price it may be the perfect choice.
Crystal Space is a 3D engine. If I recall correctly, it is portal based. I had considered it in the past and may yet use it for a future project. That is assuming I decide to develop a download only game which is probably something I should do since applet development is so restrictive. Sure there are some game engines designed to run on browsers, but their installed bases are small and system requirements are high so right now Flash and Java are the only real choices for web games.
What is really interesting about the project is that the goal of the project isn't the commercial quality game, but instead the goal is to develop a proper pipeline for developing games. This means that both Blender and Crystal Space will be improved to allow for better game development work flows.