Other
Puzzle Parlor
Find a collection of colorful, interactive, challenging puzzles: Hexnut Jr., Quintapaths, Roundominoes, and others.
Braingle
Braingle: Cryptography Brain Teasers
Test your critical thinking skills with a variety of cryptography brain teasers, phrases or expressions "encoded in some way." Solve the teasers provided at this site, and submit your own for others to try!
Other
Mystery Master: Logic Puzzles
Find several logic puzzle ranging from "very easy" to "very challenging."