The following are selection of the best British Police Car websites (plus a few US ones):

Links to follow!!

Ex Police Car Ex Police Cars for sale.
Lights-and-Stripes Ian Marlow's Emergency Vehicle photos
UK Police Vehicles John Dougal's Police Car pictures
UK Emergency Vehicles Richard Thompson's Emergency Vehicle photos
Alex McKenzie's Photos Another police photo page
John Godwin's Photos Possibly the largest Police only set in the UK.
Rescue 911 Paul Wood's US Energency vehicle photos
PVEC Police Vehicle Enthusiast's Club - for all enthusiasts