I wanted to post this, cause i haven't seen a much talk about it at all (other than bucky, god bless his heart).
Okay, so basically GBS2GB does exactly what the name says. Give it a .gbs file and it gives you a .gb file.
reasons why this is awesome:
MML/XPMCK users can easily play their GB tunes on actual hardware now.
Games made specifically for GBC can finally have their soundtracks played on the DMG's sound chip (Mega Man Xtreme, Worms Armageddon, Shantae, etc)
If you have an EMS 64mb Smart cart, you can fill up the second page with tons of soundtracks
author's webpage with a ton of other utilities
http://www.angelfire.com/nc/ugetab/
(you'll have to go to his page and do a Find for GBS2GB, i dont think angelfire lets you link directly to things)