Game Boy

BasicBoy
An open source emulator for Windows written in Visual Basic 6 and VB.NET.
http://members.lycos.co.uk/basicboy/

BGB
A freeware emulator for Windows.
http://bgb.bircd.org/

BoycottAdvance/SDL
Multi-platform emulator available for Linux, BeOS, WIN32 and FreeBSD.
http://sdlemu.ngemu.com/basdl.php

cingb
Open source emulator for DOS and Unix.
http://sourceforge.net/projects/cingb/

confusionGBx
A freeware emulator for Windows.
http://confusion.i-networx.de/

D-Boy
Freeware emulator for DOS.
http://www.emucamp.com/boukichi/

Gambatte
Open source emulator for Linux and Windows.
http://sourceforge.net/projects/gambatte/

Game Lad
Freeware emulator/debugger for Win32/DX8.
http://gamelad.emuunlim.com/

Gameboy 97
Open source emulator for DOS.
http://members.aol.com/autismuk/gameboy.htm

GameKnight
Open source emulator for Windows written in C#.
http://www.codeplex.com/GameKnight

GBE
Open source port for AmigaOS.
http://www.amidog.com/amiga/gbe/

GBMac
Shareware emulator for MacOS.
http://hp.vector.co.jp/authors/VA009321/index2.html

GEM
A freeware emulator for MSX-DOS2 written in assembly.
http://www.tni.nl/products/gem.html

GEST
An open source emulator for Windows.
http://koti.mbnet.fi/gest_emu/

GEX
A freeware emulator for Windows.
http://gex.emuunlim.com/

Gngb
Open source emulator for Linux using SDL.
http://membres.lycos.fr/frogus/gngb/

HelloGB
Freeware emulator for Win32.
http://www.emuunlim.com/hgb/

KGB
Freeware emulator for Win32.
http://kgb.emulationworld.com/

KiGB
A freeware emulator for DOS, Linux/i386, MacOS, and Windows.
http://kigb.emuunlim.com/

NO$GMB
Shareware emulator for DOS and Win32.
http://www.work.de/nocash/gmb.htm

Phoinix
An open source (GPL) emulator for PalmOS.
http://phoinix.sourceforge.net/

PlayGuy
A freeware emulator for Windows.
http://playguy.emuxhaven.net/

QuantumGB
Freeware emulator for DOS.
http://quantum.emuunlim.com/quantumgb.htm

TGB
Freeware emulator for Win32.
http://gigo.retrogames.com/

Victoly Boy
Freeware emulator for MacOS.
http://www2.hawaii.edu/~dereksmi/gameboy.html

Virtual GameBoy
Commercial emulator for Win32 and freeware emulator for AIX, FreeBSD, Irix, Linux, MacOS, OS/2, OSF/1, Solaris, and SunOS.
http://fms.komkon.org/VGB/