There are lots and lots of 3D text tutorials out there for Photoshop users and a few for GIMP. I reviewed many and compiled the techniques of those that I liked and then added some of my own ideas to create some nice-looking 3D text in GIMP. I've prepared this tutorial in the form of a pdf. so you can download it right to your desktop. Let me know your thoughts.
I do agree with a comment made before that the tutorial can be confusing at first. But I really do like the results, so thank you for taking the time and efford to do it! *thumbs up*