Yesterday I spent about 6 hours taking career tests. If you don't know what those are, they are all a little different... Basically, the tests attempt to distinguish you as a certain type of personality, worker, or interest group, and then based on that assumption they point you towards careers you will both be good at AND enjoy. I thought I'd impart the knowledge I learned onto you all.
The most helpful test I found was The Princeton Review's Career Test. Go to this site and give them your email, make up a password, and then search for the test under the career sidebar. They give you two separate results: your interest color and your usual style (all will be explained...). Both of mine turned out to be blue. The best part is they give you a list of potential careers and all are linked to a lot of info about each, including sections like a day in the life, facts and figures, graduate programs, quality of life, etc.
Another one that's really good is based around John Holland's theory, which basically says that people and work environments can be classified into six different groups (realistic, social, investigative, artistic, enterprising, and conventional). I took it here (which isn't a test you have to guess yourself which combo you would be) because I didn't want to pay. If you want to take the real test, take it here.
The third and last is more fun than anything. Its Carolyn Kalil's True Colors Test. This one, obviously, is another color based test and I thought it was very precise. I was green, which I was very happy about (I always seem to get blue on these color tests).