Wikipedia describes the big 5 personality tests

The test is based on the five trait "Big Five" test of personality and gives you a detailed printable report with a high-level view of your personality. The test is 30 questions and takes 5-10 minutes to complete. The download is completley free.

Take this psychology test to find out about your personality! This test measures what many psychologists consider to be the five fundamental dimensions of personality. As you are rating yourself, you are encouraged to rate another person.

By rating someone else you will tend to receive a more accurate assessment of your own personality. Also, you will be given a personality profile for the person you rate, which will allow you to compare yourself to this person on each of five basic personality dimensions. Try to rate someone whom you know well, such as a close friend, coworker, spouse, or other family member.