I'm a reserve officer somewhere in Los Angeles county. If you don't mind, I'd like to keep a certain amount of privacy, so I won't mention which agency There are three "big" police car sites on the net. The biggest is perhaps copcar.com. There's a lot of content in there. However, it's very hard to navigate if you're looking for a specific agency. That's why I'll recommend www.geocities.com/policecarsite/

It's quite easy to navigate and you'll find police departments classified by state, with the biggest agencies being at the top.
Have fun!