Note: I've almost got Tribes-style jetpacks working within the game, and am currently tweaking them to feel more realistic on the moon!
If you're interested in creating 3D models and content, here are some good guides:
The best book to give an exact description of how to export objects to the Torque DTS format is "3D Game Programming All In One" by Kenneth Finney. It also highlights many of the other processes I'm using in building the game.
I use LightWave 3D to build objects (but it's not free). Another great tool is Milkshape 3D (which is free). There is an entire series of tutorials at:
http://www.garagegames.com/docs/tge/ (under Tutorials -> Milkshape). I also use QuArk for creating buildings with interiors (.DIF files).
Specific tutorials to look at: