Pencil Sharpening: Braingle

"With over 7,500 brain teasers, riddles, logic problems and mind puzzles submitted and ranked by users like you, Braingle has the largest collection anywhere on the internet. Our large array of unique online multiplayer games will keep you entertained for hours. If you crave a brain teaser, mind puzzle, riddle or game, we are the place to get it. Increase your creativity, boost learning and become a better person at Braingle. Get ready to have your brain tangled!" -- from the website. <http://www.braingle.com/>