The "Bartle Test", originally created by Brandon Downey and me, now runs in a modified form on gamerdna.com. You will be redirected there in 10 seconds.

Alternatively, you can download the original English question data set -- simply ask an equal number of questions for each combination (e.g. Socializer vs Achiever) and add the numbers to get your own score.

If you want to know more, someone wrote a Wikipedia article.