Piece of Pi MadLibs - http://madlibs.freeservers.com/ Featuring a collection of madlib stories and poetry.
eLibs.com - http://www.elibs.com/ Creating interactive stories from user inputs. Possibility to add a dialect; also different categories and polls.
AskOxford: Word Games - http://www.askoxford.com/wordgames/?view=uk Cryptic and easy crosswords, fiendish word games, the history of crosswords, and scrabble and behind the scenes at Countdown.
NOVA: Decoding Nazi Secrets - http://www.pbs.org/wgbh/nova/decoding/ Crack the ciphers, send a coded message, and find out what goes on in the minds of code-breakers.
The Nautical Origins for Some Common Expressions - http://www.fortogden.com/nauticalterms.html Explaining the seafaring origins of some common words, figures of speech, and everyday expressions, like "toe the line" and "scuttlebutt".
Mockok.com - http://www.mockok.com/ A large collection of palindromes, focusing on palindromic single sentences (spelling the same forwards and backwards). Submissions welcome.
Jim Kalb's Palindrome Connection - http://www.nyx.net/~jkalb/palindromes/ A collection of links to web pages about palindromes -- phrases that spell the same forwards as backwards, like "Able was I ere I saw Elba".
Kid Crosswords and Other Puzzles - http://www.kidcrosswords.com/ Choose from several puzzles created just for kids. New puzzles each month.
Lost in Translation - http://www.tashian.com/multibabel/ Enter a sentence to have it translated from English to five different languages and back. The result is often funny; nothing like the original sentence.
Phobias - http://www.geocities.com/nallen20/FunnyPhobias.txt Article that lists some of the more amusing phobias, like arachibutyrophobia -- the fear of peanut butter sticking to the roof of the mouth.