Trainers, translations and other ROM hacks to be applied on GameBoy Advance ROM images.
Tools, file formats and techniques for editing commercial games are also discussed in GBAtemp's ROM hacking section which will have additional information for the GBA, DS and more.
Many tools are useful across systems (a hex editor works much the same regardless of the system you are working on) so do also check out the Filetrip's general programming tools section.
I feel like school, back when I was actually in school, was more entertaining though, because of how much I get to interact with people, hang out with friends, and other stuff like that. All I get to talk to at work is my boring coworkers lol