There's a nice amount of emulators out there, and it would be great to improve them all in terms of MORE FPS, MORE OPTIONS or MORE COMPATIBILITY, especially the ones with more software available for them, but I'd also like to get a decent emulator for:
Amiga
PDA/Palm (to use all the apps)
MS-DOS
I think these are kindda missing....
and Java, but I've heard Java is going opensource in the next few months so, that's on the way ;)