I have a book, and have consulted websites, to find the frequencies of my local police station, but I only ever hear dispatch talking to the officers and officers to dispatch. Never any car-to-car talk. I figure this must be a different frequency, right? But it's still accessible to the public too, right? I mean, where I live police scanners are not illegal, and as I said, the frequencies I do have were published in a book.

Does anyone know of a website where I'd find this elusive other frequency, if it's even there?

It's probably trunked. Ask google about trunking scanners if you want.

To find whatever frequencies they're using in the first place, you can either look in the fcc registry for your city or town, or again, ask google.

They tend to keep car-to-car comms trunked or digitally encrypted, so the drug dealers can't just scan in and know when they are close to catching them.