I really don't think that there are any better drug programs then epocrates, it has almost everything that you need to know about a drug. The only additional feature that I'd like to see is what percentage of people get certain side effects, but I don't think that's worth spending money for when epocrates is free.
The free epocrates is awesome. However, for more detail (but less up to date) info about certain drugs I use MosbyRx. DrDrugs and Lexi Drugs are great also.