Twitter offers the potential for a variety of learning and brain games.
Here are some examples
BeatMyTweet – “Questions via Tweet for you to beat. Reply with your answer. Check the leader boards at BeatMyTweet.com.”
ChessTweets– play a quick chess game against a friend or start a correspondence game
Fast 140 – Test your typing speed
Hot Potato – Each player needs to pass the potato before the time runs out.
Outwit Me – “your home for intelligent Twitter games .. We are here to engage your mind, to outwit you. You are here to be challenged, entertained. Each game is designed to be never-ending, stimulating.”
Plinky – Every day we provide a new prompt (like a question, or a challenge), and everyone gets a chance to answer.
Twitbrain – – “Train your brain by tweeting the answer to the challenges and earn Restecpa”
Twrivia – is a daily trivia game on Twitter
Three Twitter games you must try, Webware, 15 December 2009
5 more Twitter games to make tweeting fun, Mashable, 12 July 2009
6 Twitter games to make Tweeting fun, Mashable 28 March 2009