GBA development and emulation:

• http://www.gbadev.org : Demos, docs, and links to other interesting stuff
• http://www.devrs.com/gba : Many faqs and documentations.
• http://codewaves.com/gba/ : some tutorials.
• http://www.gbaemu.com/ : emulators download.
• http://www.bottledlight.com/ : home of mappy, a great emulator for developers.
• http://vboy.emuhq.com : home of VisualBoy Advance, the best emulator for gamers.
• http://www.pocket-dev.net : French site about GBA programmation.
• http://www.zophar.net : the emulation in general.
• http://www.pdroms.com : tons of free roms from the public domain.
• http://www.gbxemu.com : a good reference for gamers.