Word, Phrase & Fable

Bartleby.com
Best overall research tool for words, attributions, facts, phrases, mythology and pretty well anything else.

Merriam-Webster Lanuage Centre
This contains both a dictionary and thesaurus in one, which can be very handy and a real time saver. As a bonus, the site includes the transcripts of "Word for the Wise," a series of broadcast articles on words and word related subjects.

Your Dictionary.com
(Very slow loading, but packed with information.) Again, dictionary and thesaurus all in one place. Uses Merriam-Webster's. More range, however, including dictionaries in over 200 languages, plus a language "guesser" that can help determine a word's language of origin (although it "guessed" the phrase "n'est pas" as possibly being Estonian). For anyone interested in language, language theory and language use, their Library is a wonderful area.

A Glossary of Hardboiled Slang
This comes from, of all places, Miskatonic University back in 1993. Don't be a bunny, barber with the best of the yeggs.

The Phrase Finder
Can look up a phrase with just one word, or can look up a phrase for its meaning. Good, but as with so many of these phrase sites (and even phrase books), there is a limited number of phrases available.

Which means you need more options. Such as the Cliche Finder, Wilton's Word & Phrase Origins, Origin of Phrases, and the Word & Phrase Origins from Useless Knowedge.com.

Collective Nouns
Ever wondered what a collection of crows is called? (A "murder.") How about a batch of kangaroos? (A "mob.") This entertaining site gives the answer to these, and many other questions about collective nouns that you've probably never thought of. There are two categories of nouns: "submitted" which have been verified with some source, and "suggested" which is just somebody's good idea (ie: an "imposition" of in-laws).

Mondegreens
You know how everone kept thinking Jimmy Hendrix was saying "'Scuse me while I kiss this guy"? Well, that kind of mistake is called a "Mondegreen" and Jon Carroll's site has the history of the term along with an impressive collection of examples. ("Will you still need me/ Will you still feed me/ When I'm six feet four?" )