Ever fancied doing a IQ test.
If yes then try the Mensa Workout.
You can find the Mensa Homepage at:
www.mensa.org
And the Mensa Workout at:
http://www.mensa.org/workout.html
Good Luck.

Other Links:

British Mensa Homepage- UK Eire England Ireland IoM Scotland Wales

http://www.eskimo.com/~miyaguch/tops.html

http://www.us.mensa.org/