Free stuff...
Epocrates-I'd use this over any drug formulary book. Its annoying carrying too many books.
Try to get a drug rep to get you a free DSM IV-TR handbook that you can carry in your pocket. I got the DSM on my palm pilot, but I prefer to keep the book on me. The way the palm version is done, you have to click and find info that is all on the same page in the book version. I find the book version more user friendly.
Most programs reccomend a Kaplan & Sadock. While I too reccomend it, I would try to wait & see if you could get one for free. This book is expensive and is often offered for free by drug reps. Why pay for it? Trust me, its not like your program will pimp you on the info in the book immediately. At least mine didn't.
Stuff to buy...
Psychiatry ON CALL. IT has pretty much every situation you'll need in Psychiatry down pat for you.
Most of the palm stuff I've tried--and I tried a heck of a lot of it, I didn't find helpful for psychiatry. Oh yeah it was useful for medicine, but not psychiatry.
Anyways, since you got to do a few months of medicine anyways...these palm programs I reccomend...
5 minute Medical consult for palm
5 minute ER consult
A to Z drugs