A zanny, thought-provoking collective of riddles, puzzles, and equations to baffle and stump your mind.
The Grey Labyrinth: the place for mental calisthenics.
AIMS Puzzle Corner: a new puzzle each month
Puzzles for the Mathematically Intuative
Brain-Teasers whose words, shapes, and positions can be used to derive a word or saying.
Riddles: the almost unsolvable kind. (Although good, it is slow)
The Quest to find the Brain of the Internet.