Davis's Drug Guide for Nurses:
This is the best PDA drug guide I have found. A lot of the others are designed for physicians and do not have info nurses need to know, such as IV compatibility. I can't tell you how many times this has saved me from running back down the hall to the nurse's station to find a drug book because I couldn't remember whether cipro was compatible with morphine.
Taber's Cyclopedic Medical Dictionary:
Is there a nurse out there who does not own or use Taber's? I have found Taber's to be most valuable when I have a patient with a medical condition I am not too familiar with, but it has been helpful for looking up all sorts of things.
These are the only references I have purchased. At $50 each, they are not cheap, but I have found them well worth the money. I got them through Skyscape; there are other vendors that sell the same references. There are many free medical references available also.
I bought the TX to use at work, but I must admit that I have used it for entertainment more than I have as a medical reference tool. Hundreds of games, many free, are available for the Palm platform. It is an mp3 player and video player; one person I know has the entire Lord of the Rings trilogy on his TX. It has wi-fi and can be used to surf the web at any wi-fi hotspot. And of course, it handles all the PIM (Personal Information Management) stuff beautifully.
It is not a phone; if you want a PDA/phone combo, consider the Palm Treo or smaller Palm Centro. Personally, I prefer keeping my gadgets separate; I'm perfectly happy with my little dumb phone. And the TX has a much larger screen than any smartphone, which makes it better for references and for gaming.
To learn more than you would ever need to know about PDAs of all types, check out Brighthand.com. The friendly, funny, helpful and knowledgeable folks there can answer even the most obscure questions.