I use the Hospital Drug Formulary icon on my work computer. Unlike a book, the lists add new drugs and are kept up to date.
I still have my 1998 Lipincott manual I bought when I started working, it is kept for sentimental reasons.
I have not re-upped my Skyscape for several years. I just use what's there. It's good for admin detail because it's of a nursing sort of understanding. Other than that I have Micromedex and Medscape and Epocrates (which, I almost never use).