Since Wordplay has come out, crossword puzzles have been on the rise. If you want to join in on the fun, read this primer by Will Shortz to get started, then download Across Lite, head to Cruciverb, and do free puzzles in the right-hand sidebar. Will Johnston's page contains a huge repository of Across Lite puzzles. If you get stuck, can't figure out why an entry is correct, or just want to chat about a grid's brilliant construction, try reading the crossword blogs. The best two are Diary of a Crossword Fiend and Rex Parker Does the New York Times Crossword Puzzle. (Caution! Spoilers abound!) And, if you want to try your hand at constructing some crosswords of your own (submission guidelines for various papers here), Crossword Compiler is an outstanding piece of software. [Via this AskMetafilter question]
Labor Intensive is a new online puzzle extravaganza in the style of the MIT Mystery Hunt and the aforelinked Puzzle Boat. Appease the Gods by performing twelve puzzly labors. Good luck!
Etymology-wise, which hormone is an island? What word both denotes a prime and euphemizes Satan? What word denotes "the future" and abbreviates the unknown? Is urine pith? These are some of the questions from "Moot: The World's Toughest Language Game," a homemade and little-known board game for lovers of words. Some puzzles are available online; there are a few more available on a page detailing the interesting story behind the game's creation. You can sign up to have a new language puzzle e-mailed to you every week.