Some Gameboy emulators...
No$gmb (Nocash Gameboy) http://nocash.emubase.de/gmb.htm
This is one of the best and fastest gameboy emulators around. Its builtin debugger is very useful for programmers. Downsides are sound and the fact that Gameboy color emulation for more than 3 minutes cost you money. (It's well worth the money if you're a programmer)
Visualboy Advance http://vba.ngemu.com/
Despite the name this program emulates both GBA and Gameboy Z80 games. Its support for commercial games is good (In other words, it runs LSDj). Works on all modern platforms (Windows, Mac OSX?, Linux, Be OS...). Can record. WAV files straight from the emulator.
BGB Very accurate Game Boy emulator! http://bgb.bircd.org/
Runs on Mac OS, Linux, Windows (i have this working fine on os x 10.4.9 it lets you record .wav files straight from the emulator)
Virtual Gameboy http://fms.komkon.org/VGB/
VGB is known for its bad compatibility, but it might have been improved lately? However it's portable and may be a good alternative for Mac and Linux users.
GB emu for GBA. With Pogo Shell and some Backup Gear you can run LSDJ on a GBA SP! kit samples are noisey (because of GBA sound hardware — not goomba ;), and the screen updates can lag — but definitly usable for live sets!
NOTE: at the time writing (dec 2004) Goomba can't run LSDJ v3 and up because of SRAM incompability! Please complain about it here: http://boards.pocketheaven.com/viewforum.php?f=29 /johan
UPDATE: there now (mar 2007) are some v3 LSDj releases patched for Goomba. but they will only allow one song for each save. /johan
Goboy N-gage http://www.wildpalm.co.uk/GoBoy7650.html
Gm emu for series 60 phone. Promising that beautifully loads the main screen and the sound does not work at all. May work better on other phones, but even if it did, it would be in mono and something like 22khz (ideal for an mp3 death release...)
Javaboy LSDJ On this page you can have an online LSDJ overview and try some features. http://www.retromundi.com/try-lsdj-online.html
Lame Boy DS Game Boy emulator for Nintendo DS. http://www.google.com/search?q=lameboy+ds
Wii RIN Port of the PSP emulator. Use the Goomba version. Sound works pretty good. Wiimote Support http://mirakichi.hp.infoseek.co.jp/software/RIN_Wii.html
Emulation for Android As no information exists currently I am taking it upon myself to better this space, feel free to edit with some suggestions on reliable decent sounding emulatiors on android. This is post gameboid so my review of what I find will follow soon.