The Grey Labyrinth (Popularity: )

A beautifully illustrated collection of puzzles, riddles, and paradoxes. Features a changing "unsolved puzzle" plus three years worth of previous puzzles.
Category: Games\Puzzles\Brain Teasers

Free PC Puzzles (Popularity: )

Small Windows entertainment set specializing in jigsaw puzzles but also containing arcade, casino, and trivia games.
Category: Games\Video Games\Freeware\Collections

Just Optical Illusions (Popularity: )

Focus on geometric optical illusions by Gianni A. Sarcone and Marie J. Waeber
Category: Games\Puzzles\Brain Teasers\Optical Illusions