AmplituDS v3 is now released. A huge update over v2 which improves graphics, feel and adds 3 new stages.
If you don't know what the game is about, it's based on Amplitude for the PS2... which was created by the team that made Guitar Hero later on.
The official AmplituDS website: http://amplituds.drunkencoders.com
Now, as for the model converter and viewer.
They both run on the NDS. How's that for portability?
The converter converts models in the .x format of a certain syntax to a .c file which contains a display list in an array.
You could use that .c file in your own homebrew projects.
The model viewer reads out that .c file, and also slaps on textures if you've put that in the same directory.
Check it out. It's worth it.