Are you a budding programmer (like me), who would like to gain yourself some fame and fortune, by writing an emulator. Here are a list of those gaps in the market, that I've recognised by people asking me if there is one available. If there are any you'd like to add, then please drop me a line.

VPCE - now Paul Cliffords unable to port it, could someone port v0.30 please?
SNEeSe - Snes9X is great, but this emulator in C is begging to be ported.
CPC - Mark Rison is looking for someone to take over his project.
Atari Lynx - there is one available for other platforms.
Fast NES emulator - xNES is still quite slow so an ARM code emulator would be great!
Megadrive - MESS is too slow, but an ARM code emulator is in the works.
Sinclair QL - there's one for other platforms, and part of the source is available, see technical links for details.
Vectrex
Freeware BBC emulator - needed since 65Host doesn't run on a StrongARM. Source code is freely available for BeebInC
Freeware PC emulator - If you want a challenge :o)
NEO GEO - MAME is far too slow and RAM hungry, the PC has much faster alternatives, why don't we!?

If you need some more info, take a look at the technical documents area.