The dictionary of obscure sorrows
Ennuitastic.
Tags: dictionary
Lexadecimal
Hexadecimal colours and their corresponding dictionary definitions. Cute.
Announcing Typo.js: Client-side JavaScript Spellchecking
This could be a handy: a client-side spellchecker. The dictionary files are a bit big of course—maybe local storage could help.
Addictionary :: What's your word?
It's The Meaning Of Liff all over again. Creating and rating neologisms.
The Septic's Companion - A mercifully brief guide to British culture and slang
British English slang dictionary with translations into American English.
Science Fiction Citations for OED
Put all those years of reading science fiction to use. Help track down first usage of sci-fi terms.
Merriam-Webster Online
The word w00t has been voted Merriam-Webster word of the year 2007. Slow year.
Happy Cog Studios: Work: Dictionary.com
Happy Cog redesigns Dictionary.com and its siblings.