Well guys, I'm not trying to brag but if you're interested in running emulators on your modded xbox then I'm your huckleberry.
I've got practically every emu working perfectly on my xbox. If anyone has any questions about getting one working lmk.
I also wanted to respond to the linux PSX emu. It's true that with quite abit of hassel you can get it working but it's impossible to get the controller setup within linux and there are sooo few people using it that you're not going to get any help. So my advice is to use the PCSXbox emu which Xport recently updated to v18 and now runs almost every PSX game.
I know alot about the PCSXbox emu because I help test the games for the guys at Xbox scene who keep track of which games work and which don't. Here's a link to the thread. They even gave me some props for testing so many games.
http://forums.xbox-scene.com/index.php?showtopic=238506
Here's the Xbox Emu's I've got currently working:
AbuseX- Emulates for the game Abuse, which i believe was the first incarnation of Halo
AdamX - Colecovision
MamedOX - 100's of Arcade Games
z26x V.4 - Atari 2600
A7800x - Atari 7800
MednafenX Lynx v2 - Atari Lynx
Blissx - Intellivision
dosxbox - DOS, my personal fav because it's the only way to play X-COM on the XBOX.
FBA XXX PRO - 100's of NEO GEO & Capcom games
fmsxbox - MSX
Killer Instinct XXX - Killer Instinct
Namco Museum - Vintage Namco Collection
NeopopX - NEO GEO Pocket
MednafenX NES V8 - NES
Surreal64 XXX - Nintendo 64, they finally updated this emu so it actually plays quite a few games now. Tetrisphere is awesome!
Xboy Advance V21 - Gameboy
OpenBoR for Xbox - Beats of Rage
PCSXbox v18 - PSX
MekaX V1 - Sega Game Gear
Neo Genesis - Sega Genesis
Shadow Warrior
SpeXtrum - Spectrum
Super Mario War v 1.7 B3
ZsnexBox V3 - Super Nintendo
MednafenX PCE - PCE Turbo Graphix16
ViceX - Commodore 64
WinstonX - Atari ST
WinUAEX - AMIGA
And last but not least XMUGEN which is a complete beast. In order to get it working you need to configure it, this is where most of the problems arise. Linux is cAsE SenSiTiVE and if you make even one error then mugen will crash.
Guybird has made the best xbox mugen so far because it doesn't crash and it's almost idiot proof. Soon he should be done with the Ultimate pack, which is a huge character screen of nearly 1,000 characters to choose from. ie. Homer Simpson vs Naruto If you want to DL his pack you can find it at Xbox Sky.
There are still more emu's but atm, I've only got a 200 gig for my emu's so once I get another modded xbox I'll replace the 200 with a 320 gig perpendicular drive then I'll have enough space to fit all the rest of the emu's. It's really just the PSX that take all the space. My pcsxbox folder is over 120gigs.

Eat dat melon biotch!
Systems Owned: Xbox, Dreamcast, Saturn, N64, PS2, Genesis
Systems Emulated: Xmugen, PSX, GameBoy Color, GBA, Genesis, NEO GEO, Turbo Graphics16, MameOX Arcade, N64, Killer Instinct, Super Nintendo, NES, Gamegear, Intellivision, Colecovision, Atari, DOS