You can find the frequencies for your local area on the Radio Reference database:
http://www.radioreference.comUse of the database is free and the information is generally updated frequently.
Use this to decide if you need a fancy digital scanner or whether a less expensive analog-only model will do the job.
Here in Colorado, the State and many of the cities and counties have gone to the trunked digital system so that pretty much dictates an expensive scanner. Depends on what you want to listen to whether there is a problem or not.
There is also a thing called "rebanding" going on where many existing systems are being changed in their frequencies. In many cases these new frequencies can't be recieved by current model scanners. (700 Mhz area) Colorado is in transition.