Nanowrimo.org: official home of the National Novel Writing Month. 50,000 words in 30 days? Bring. It. On!

Wikipedia: if I could pick only ONE resource to recommend, it would be this one. The wikipedia is fantastic for looking things up!

Encyclopedia Mythica: a wonderful resource for looking up classical references, also covers Eastern mythologies and many others. Wonderful site.

First Line Generator: got writers' block? Try a pre-generated first line to see if it helps solve your blockage!

Information Please: combination encyclopedia, dictionary, and other reference works.

20,000 names.com: an excellent resource for finding new and exotic character names. Names are sorted by nationality and meanings of names are included. The site may have some popups so be prepared for those.

The Mary Sue Litmus Test: concerned that your character may be a Mary Sue (or Gary Stu)? Take a walk through this quiz page and see how the measure up. At the very least it's a very amusing test to run through!

Printable Calendars: trying to plan out events in a story? Print out a calendar to have handy so you can pencil in dates and times and keep your timelines from splitting! Unless of course, you're writing Sci Fi, then split away!

Rhyming Dictionary: just what it says. For the poets who don't yet know it.

Spelling Checker: for those times when you're not writing in a word processor.

They Fight Crime: an HYSTERICAL writing prompt generator! He's a jaded hunchbacked messiah from the Mississippi delta. She's a time-travelling winged widow with someone else's memories. They fight crime!

Word Counter: need exactly 100 words? Check your word count here.

Synonyms: for when you need a word that means the same...

Seventh Sanctum Writing Prompt Generator: again for those times when you're just totally blocked. Generate a prompt.