Here are a few links which helps me and probably you to find out more about trueSpace.

The german trueSpace forum - das deutsche trueSpace Forum

The international trueSpace forum

Moonmans trueSpace resource site - not actual at all but a good starting point to find plugins, shaders etc.

The trueSpace TSX archive. A lot of plugins and tutorials about it can be found here

An ever-growing list of tutorials for trueSpace