Symcat is a web service that will attempt to diagnose what ails you. All you have to do is type in your symptoms, and the service will try to match it to diseases are most commonly associated with your collection of problems. It can be quite helpful for doing research, but you definitely want to consult a real physician before deciding you have cancer or bubonic plague.
There are hours of amusing fun to be had here plugging in symptoms and seeing what comes out. As long as you aren't a hypochondriac, in which case you will immediately have a meltdown when you find out that a sore throat could be a cold . . . OR IT COULD BE ACUTE RESPIRATORY DISEASE. You can also watch people's symptoms in real time, to find out if everybody in the world has achey toes today. Which apparently they do, at least when I last checked.
Go ahead — try out Symcat.