A mod/s3m player with source. THIS is the player you want to pick up if you're doing a 100% asm intro with Tran's pmode v2.xx and need SB support. It's easily tweakable to play your tune from memory, though the code given loads from disk. If you don't need SB support, also check out Robban's GUSPlay.
Reads a 3ds file and outputs an easier to read format. Good utility with full source for reading .3DS files. It's easily tweakable (with a #define) to read from a file or memory and not that difficult to tweak for your own 3d structures. It's also done well enough that adding support for more features of the .3ds format should not be that difficult from a coding standpoint. Specs are admittedly hard to find.