Which word game should you play?
For a quick game, the Word Guess Game, Hangman or Word Scramble. If you like sorting and connecting, Word Groups; if you like clues, the Mini Crossword or the Cryptogram, a sentence in which each letter has been swapped for a different one. Word Ladder asks you to change one letter at a time, and Word Wheel to find as many words as you can in nine letters.
The Reading Speed Test times your reading in words per minute, then asks three questions about the story so a skim doesn't count, and the Proofreading Test asks you to spot the mistakes in a passage. The Semantic Priming times something smaller: how much faster you recognize a word just after a related one.
Where do the words come from?
From published word lists. The hidden words in the Word Guess Game and Hangman are common words taken from SCOWL, the lists spell checkers are built on. Word Wheel, Word Ladder and Word Scramble accept a word if ENABLE has it: a word-game list released into the public domain. The Mini Crossword's clues were all written for this site.
Can you play as many games as you like?
Yes. There is no daily limit: the Word Guess Game hides a new word every game, and Word Groups lets you play as many sets as you like. Nothing to download and nothing to sign up for.