VisualBoyAdvance

VisualBoyAdvance Sourceforge site - for those wanting to do ports, report bugs, request features, etc...
EasyEmu - contains tutorials, including one for VisualBoyAdvance

Skins for VisualBoyAdvance - contains skins and a skin creation tutorial
VisualBoyAdvance site - Skins
Advance Boy skins - More skins

Computer Emulation Resources - Lots of tips on writing an emulator
Emulation Programming Resources - Lots of technical information
Programmers's Heaven - Lots of programming resources for different languages

Aldo's GBA-SDL
EmuShadow
GBA Shell
GnomeBoyAdvance - Linux GNOME frontend
qtvba Qt based frontend for VBA

DevKit Advance - GNU Tools necessary for GBA development
Gameboy Advance Development - Demos, documentation and link to other interesting stuff
Gameboy Advance Devrs - Great site by Jeff Frohwein with FAQs, samples and more
GBA Emulation News - News on GBA emulation
HAM Development Kit - A development kit for the GBA for Win32 systems.
The PERN Project - Tutorials, demos and examples.

Public Domain Roms