What emulator would you suggest exploring after MAME? I grew up in the prime time of coin-on operation, so most of the rest of the system emulations are a bit foreign to me.

SNES and Megadrive
Edit: Not to mention Neo Geo.

NeoGeo then.
Also if you haven't tried the various consoles, then you are missing out on some real gaming gems!
NES,SNES and MegaDrive are highly recommended

You have to get Picodrive and GPFCE, those are 2 awesome emulators on GP2X. GNGeo is awesome too, even more so now with the performance boost its being given

CPS2, for the twitch-shooting good time, every time

There's some fun to be had with the GBA emulator.

Here's the link to the latest release: http://notaz.gp2x.de/misc/gpsp09-2xb_2.zip

Just in case the latest release isn't in the File Archive.

Thanks, SiD. My version was older.