The Spectrum allways had quite a few emulators, because of
his simple construction. MacOSX has a conversion of the
Free Unix Spectrum Emulator, Fuse.
Fuse
There is a new spectrum emulator, ZXSP, looks quite tasty
For your dashboard, there is one too. Ideal for a quick
game, e.g. of Cracker, the Eurogamer christmas gift i mentioned,
you can find the widget here
There is a great new way to play old speccy games on your
Mac. MySpeccy adds an online dimension, with global
leaderboards and stuff. It is almost Xbox live. It works
with Java emulation, but really speedy.
My profile page: Romanista
The predecessor of the Spectrum, the ZX81 can be emulated
using Mess
For those of you with a DS, and a flashcard, don't for get
the great SpeccyDS