This is a list of systems that don't have a driver for MESS yet, but ROM images are available.
Performa 630: 68040, max. 36 MB RAM
Second processor board for the BBC Micro. http://members.lycos.co.uk/leeedavison/z80/torch/
Roms are available for this, should be a simple drop-in
Other emulators and docs at http://community.computerhistory.org/scc/projects/FORTRAN/index.html#Simulators
(this is the system which first used the Power processor, later known as PowerPC)
Z80, CP/M based “business” computer
Emulated in mednafen.
As a SNES driver with added hardware to emulate the Game Boy features.
European successor to the Videopac G7000, was intended to be released in the US as the Odyssey³ but never was (although prototypes exist). Emulated by O2EM.
Originally sold for ¥33,800, was an upgraded version of the SC-3000 with more RAM and an upgraded keyboard (the original keyboard was of the low-end membrane type).
Don't know the CPU speed, but 200Mhz is a good guess.
(at the time, Sinclair Research Ltd was called “Science of Cambridge”)
Emulated and described in Paul Robson's page.
Original manuals and schematics are available here.
Is on Wilbert's list of things to do. Neo Geo Pocket mono bios still needs to be dumped
Note: will require an NEC upd772x cpu core (which is also needed for once the dsp-1 and so snes roms are decapped out, and is needed for sega 'air rescue' in MAME anyway)
(both of these will require some type of Votrax SC-01 emulation. whether that is done via sample concatenation or actual emulation is up to whoever writes it)
(these two are really peripherals, they lack cpus at all. discrete emulation will be necessary for both, but is significantly less hairy for the TRS-80 speech module)
(lord_nightmare attempted to get a driver working for this but is horribly confused by the way the mame/mess rom/ram banking system works. He has information on how to probably get the system booting and where the i/o regs are for various stuff. keyboard input is still unknown, same with alt peripheral input such as mouse, touchpad, touchpanel, etc.)