http://tezxas.ticalc.org/

It's by the same guy who (co)wrote Warajevo, a Spectrum emulator for PCs concieved under the worst conditions possible (complaining newbies on message boards and hatemail pales in comparison).
http://www.worldofspectrum.org/warajevo/Story.html

Anyway, someone should try to get Samir interested in MAME..writing a working/playable emulator for a Z80 system on a 68000 based system is an impressive feat.

-Sune