VisualBoy Advance (vba.ngemu.com)
Currently the most well known and widely used Gameboy Advance Emulator. VBA seems to have the least amount of trouble running all the latest GBA ROMS. It even includes features for using Gameshark, and Codebreaker on your GBA ROMS, without even have the cheat devices. It offers many features including multiple save type support, and has debug modes for trouble shooting problems.

VBALink - VBA Link
VBA Link is a modified version of GBA Emulator VisualBoy Advance that now supports GBA/SP multiplayer link cable emulation and linking of up to 4 gameboy emulators with gba roms New! Works on one PC or you can take advantage of LAN support and connect up to 4 PC on the net. . At this time linking is possible only under Windows OS.

Boycott Advance (boycottadvance.emuunlim.com)
If there was a second place prize for Gameboy Advance Emulators, Boycott Advance would most certainly take it. For a long time, this was my emulator of preference. It pretty much contains all of the features offered by VisualBoy Advance, but just hasn't been as well built up by word of mouth. If are having any troubles with the VBA emulator, be sure to give Boycott Advance a shot!

RascalBoy Advance (www.rascalboy.nzone.it)
Another one of VBA's close competitors. Rascal Boy has become one of the better GBA Emulators currently available. A feature particularly nice about RascalBoy Advance is that it supports ISP Patching. Forgetting downloading a bunch of programs to patch your GBA ROMS so the saves work or you can have trainers (cheats)... just get RascalBoy Advance and it will do all the work for you!

GBXemu - Gameboy Advance Rom Backup Resources

Game711.com (game711.com/gba/english/)
One of the most well known GBA sites offers roms. Game711 was a very good resource to download GBA ROMS. Adding all the newest GBA ROMS as they are released. They went down for a while, and now they are back up! The site is quite slow, but they still have a decent selection of Gameboy Advance roms to choose from. They are a little behind though with keeping up to date. The roms are usually not up to date, but there is quite a large selection to choose from. If you are looking for older GBA ROMS, try here.

EmuVortex (emuvortex.net)
An organized site with all the latest GBA ROMS. So far they have all roms from number 0001 to present. Updates are very fast, with screenshots showing each rom. Download speeds are very fast, rom variety is huge! Site requires you to register in the forum in order to download GBA ROMS.

G-Masters (g-masters.com)
Has all GBA ROMS from 0001 to latest. Rom servers sometimes down, but there is an alternative server to download off of. Downloads speeds are average. A registered account in the G-Masters forum is required before being allowed to download GBA Roms off the server.

ChinaGBA (chinagba.com)
This site has tons of GBA Roms, but they are sort of mixed and matched up. They seem to have all of the newer GBA ROMS, including pictures of the GBA ROMS before downloading. No username or password is needed to download. Decent download speeds. Only downfall is that the site is in Chinese so its sort of hard to navigate through sometimes.

GBXemu - Gameboy Advance Emulation and Rom Release Info

Pocket Heaven (pocketheaven.com)
One of the best GBA infomational database centers on the net! Pocketheaven hosts many of the best GBA information sites there is. A collection of data on rom releases, game patches / trainers, emulators, and much much more!

Pocket Heaven - GBA Releases (releases.pocketheaven.com)
A sub-section off of Pocket Heaven. This is the official rom release database for all GBA ROMS dumped on the net. Updated within minutes of each rom release, it is a great place to find out if your roms have been dumped on the net yet. A complete release list is available showing all roms ever dumped, along with screenshots, NFO's, boxart, and rom information.