Hi firechick. Welcome to the Pre-Hospital section of SDN.
I owned a PDA when I was a paramedic. Back then, there wasn't much available related to EMS except a medication guide. I used it primarily for the calendar and address book.
There are programs that you will find useful: a drug reference (such as ePocrates), useful for looking up what a drug does and also good for dosing for some of the drugs you carry; EMS guides (various ones produced), good for general guidelines; drip calculators, good for when you become a paramedic.
Most of the uses of a PDA are pretty high-end for physicians and nurses, but I think you will find some use from it. Just having a calendar and address book on the thing makes it very useful. If your cellular provider supports internet access, and if you have a Bluetooth-enabled cellular phone and buy a Bluetooth-enabled PDA, then you can surf the web, get your email, and even access AOL Instant Messenger from your PDA. (Nothing like doing these things to eleviate boredom while stuck in some parking lot sitting in your rig.)