Medscape eMedicine

This website has everything you want to know about a disease. Causes, risk factors, diagnostic investigations, Symptoms, Complications, etc etc etc. Definitely bookmark this and have it for your Clinical Rotations. Looking up medication names and dosages are essential!

http://reference.medscape.com/

Also, you can get the app for free on your Ipod/Iphone/Ipad/Android/Blackberry:

http://www.medscape.com/public/mobileapp

It's great, I once looked up an analgesic I almost bought from a Pharmacist in Africa, and it turned out I was buying an antibiotic, so I gave it back.  

It also will give you all the pharmacokinetics of drugs, drug-drug interactions, and new updates and articles + more. Highly recommended for anyone in the medical field.

Remember to be connected to Wifi at first, there are a lot of updates to load
but after that, its very fast and doesn't need to be connected to the internet.