A technology which takes a sort of middle ground between traditional book publishing and purely electronic forms such as web publishing and e-books. It has many advantages for the writer, including larger royalties and the retention of rights, so I will definitely be keeping an eye on this during the next few years.
Books and Tales - An Incomplete Guide to Print on Demand
Let's face it, even experienced writers have questions, or need a nudge in the right direction every now and then...
The Free
Dictionary - My new preferred online dictionary and thesaurus. I
used Dictionary.com and Thesaurus.com for a while, but then they
"upgraded" and broke most of the features I really liked.
So I went out and found this one instead, which I think is actually
more comprehensive and useful in a lot of cases anyway.
Jack Lynch's Guide to Grammar and Style - A thoroughly useful and accessible resource on the subject of grammar, word usage, and stylistic issues.
Common Errors In English - Pretty self-explanatory; this is the place to go when you can't remember under what circumstances to use an apostrophe in "its," or how exactly hyphenation is supposed to be done.
Articles on Writing at the Science Fiction and Fantasy Writers of America site
"How to Write" by Robert J. Sawyer - A friendly and comprehensive writing guide, with attention given to the peculiar issues faced by authors of speculative fiction. Also includes information about the process of traditional publishing and tips for writing cover letters, outlines & synopses, etc.
Science Fiction & Fantasy Writing - Another speculative fiction writing guide
Sexual Tension - A very good essay on what it is and how to make effective use of it in a story. It's geared toward romance writers but would (IMO) be a useful read no matter what genre you work in.
These are sites that I have found useful for various aspects of worldbuilding.
Wikipedia.org - One of the best general references I've encountered on the internet
Animal Diversity Web at the University of Michigan's Museum of Zoology site
Everyday Life in the Middle Ages - Self-explanatory
Classics Technology Center - This is a great basic reference for many ancient cultures, including Egypt, Classical Greece, and Imperial Rome
Greek Mythology Link - Everything you ever wanted to know about Greek mythology
Athena Review - Lots and lots of info on ancient cultures and current archaeology
These are sites where the information might not be based in actual science, as such, but are still useful to the writer of speculative fiction.
The Pagan Library - Need information on all the myriad varieties of paganism, or a jumping-off point for a ritual or rite of passage in a created universe? You can probably find some good ideas here.
WinterHome - A nice site with information on some of the trappings of witchcraft. I find the listing of powers attributed to different types of stones and crystals particularly useful.
Babynamer on Oxygen.com - Need a character name that means something specific? This is one of the more useful of these search engines that I've found online...
Behind the Name: First Names and Behind the Name: Surnames - Two more excellent character naming resources
Dream Dictionary - One of the most useful and comprehensive online guides to dream imagery and symbolism that I've been able to find.
Astrology Zone - Whether you believe in the subject or not, the personality profiles here are very interesting and could be a useful resource for character development.
Most people who write speculative fiction will have to deal with a constructed language sooner or later; here are some sites that you may find useful in that regard.
Language Construction 101 - A short and sweet guide to making up a language.
The Language Construction Kit - Lots of info here; beginners may want to brush up on linguistics terms before diving in, which can be done at the next site listed...
SF Xenolinguistics - A page with the science fiction author in mind, but not for the humor-challenged