Official site
(for the record, this site was here first, and they have copied from me!)

Internet Movie Database

Smack The Pony and related stuff:
Official Channel 4 microsite
Big Red Tractor Smack The Pony fansite- now defunct?
An interview in the Guardian
Sally Phillips- a little web page

The other cast members:
Ronan Vibert- Japanese fan site including a Gladiatress gallery

Something a bit weirder?
The Smack The Pony page on the Female Celebrity Smoking Database (and here's an NHS smoking helpline)

This fan site was created by Stuart Bruce.