This is the link repository of the if2a website. You'll find various sites of interest related to GBA development in general.
The reference site/forum for Gameboy Advance development. Highly technical with lots of experienced and talented programmers, some of them belong to official GBA development studios. Also hosts a Nintendo DS development section. Be sure to check out the development competition !
Emuboards is probably the biggest forum community around emulation in general. Various subjects of interest, from Pogoshell, Nes and GBA to less common devices such as the GP32, Zodiac and Gizmondo. Both newbies ana experimented people. Nice community.
Smaller then Emuboards, PocketHeaven is nevertheless very active and hosts prestigious support forums such as the ones for Goomba, the GB emulator and PocketNes, the Nes emulator. More technical than Emuboards.
Great french community and development forum! Also hosts a small english forum section. Nice place to be. Great homebrewn authors.