Epocrates is offering their $159 Essentials version free to medical students during the month of August. Go to this link to download the product to your mobile device- http://www.epocrates.com/e/FreeforMedicalStudents2012.
Epocrates Essentials‘ “all-in-one clinical reference suite provides you with drug & disease monographs and diagnostic tools. The evidence-based disease content distinguishes this suite from Epocrates Rx.” (Epocrates Rx is always available for free from Epocrates.)
You can find out more about the different Epocrates mobile products here – http://www.epocrates.com/mobile.