A software for creating crystalspace contents
It provides all the tools to manage your assets, build scenes, make use of entity systems, add logic, live program your world, etc. Of course, you can also do this in a cooperative way : CrystalArchitect supports networked editing, which is a blessing for teamwork.
On top of that, CrystalArchitect supports as many 3d engines as you want, with currently an emphasis on Crystal Space and CEL.
Using CA, you've got a perfect workflow to start from raw art, let your imagination create what you want and export your newly world to a coherent and complete software package.
(note this is temporarily also the webpage for CAF, the framework on which CA will be based)