Whether you're trying to figure out what's wrong with you (healthwise), locate a pharmacy or hospital, learning about drugs and treatments, or track your health problems, WebMD is an extremely comprehensive solution for all of those tasks.While probably an enormous time-waster for hypochondriacs, if you're trying to figure out what's ailing you WebMD's mobile app for iPhone and Android is helpful. You can specify symptoms easily by tapping the part of the body where they exist, and then once you've finished adding them all the app will identify some possible problems. You can then save those conditions for later to keep track of what you've discovered — perhaps for when you're seeing a real doctor to verify.
The WebMD app also lets you check out drugs and treatments, so you can learn more about them, and provides photo and video content to help you learn about things like CPR. Additionally, if you're looking for a local pharmacy or healthcare provider, it'll help you search using your current location (or any other location you want).
The only potentially major downside is that the app is a little slow to launch, but that seems to be more of a problem on older hardware. On the iPhone 4, it loads in just a few seconds.
WebMD is available for free, right now, for iPhone and Android.