Get a PDA of some kind, and put Epocrates on it. This free downloadable PDR gives all the essential information: drug names (brand and generic), indications, dosing, adjustments for renal/hepatic failure, side effects, contraindications, interactions, and pharmacology. There are also some nifty medical calculating gadgets that come with it, which will calculate FeNa for you, calculate equivalencies between different narcotics or steroids, and other mysterious details.
This program is tremendously useful for those times when, as usual, the patient gives you some funny spelling of their medication, or only knows the brand name and it’s a very tiny brand, or can’t remember the dosage. You can look up variations on the names, and find out what the usual doses are (if something only comes in 10 and 20mg, it’s very unlikely that they’re taking 300mg of it).
It’s also good for cancer patients being admitted for other reasons. The chief or attending will invariably ask what chemo regiment they’re on, and if you’ve run all the strange-lookings names on their med list through Epocrates, you can look brilliant by saying that they’re on X tyrosine-kinase inhibitor and Y mitogen inhibitor (which is usually used in advanced renal cell carcinoma, but has a new indication for this tumor).
There are some other good PDA applications, like the Johns Hopkins Antibiotic Guide (you can search by type of infection and bacteria involved, not just the name of the antibiotic), but to my mind Epocrates is the only really essential one. It’s gotten so ubiquitous that people really expect the interns and med students to have it available to solve problems with.