spectemu is quite a nice 48K Speccy emulator. It doesn't emulate the 128K machines though. I use Fuse (the Free Unix Spectrum Emulator)
which emulates just about everything, including a black and white TV
This is the main Fuse site where you can download the source code:
I installed the Debian binaries available at
though rather than compiling from source. Works fine here on Gutsy.
Here it is running one of the best Spectrum games ever.