As I include several online generators, rhyming dictionaries, and other writing shortcuts here, I feel the need to stress that none of these are a replacement for thorough, thoughtful development and writing, but are intended as a jumping-off point for inspiration.
Grammar and Style
Keep in mind that the rules of grammar and style vary and can often be bent.
GrammarBook.com – I have found this to be a really good general reference for grammar and punctuation.
Grammar Girl – Part of the “Quick and Dirty Tips” series; site and podcast with answers to common grammar questions.
The Purdue OWL (Online Writing Lab) – This is mostly a reference for technical/academic writing, though there is a creative writing (mostly poetry) section. It has many more in-depth articles about grammar, mechanics, and style than GrammarBook or Grammar Girl.
Wikipedia – American and British English Differences – Usually I don’t trust wikis and sites that rely entirely on user-made content, and It’s quite thorough and fairly technical, but also a little confusing to just browse through or find something in particular.
Dictionaries, Thesauri, Etc.
Reference.com – Home to Dictionary.com and Thesaurus.com. I used to shy away from this site in favor of online dictionaries made by the publisher of the book themself, but it is quite excellent to cross-reference various sources.
WriteExpress Rhyming Dictionary – My favorite online rhyming dictionary. Gives you a very large output and a choice of four different types of rhymes.
Merriam-Webster’s Word Central – The rhyming dictionary here is more selective in what it outputs with some, but not all, of my test words, though it doesn’t give you the options of types of rhymes. Oddly it is not a feature of their main site.
RhymeZone – This was my standby for quite some time. It gives you a very large output, but a lot of it is words with no real use or that are just weird, especially when phrases are turned on. Still, it can be interesting to see what it gives you, especially when you’re really stuck.
The Online Slang Dictionary – Has some of the issues shared with anything user-generated, but a decent compilation of slang terms from various regions and demographics. It also has a meter of how vulgar a term is, how common it is, and where it is used — really good if you’re writing a demographic you aren’t immediately familiar with.
Characters and Naming
Behind The Name – A great reference for finding names for characters, or for personal use. In-depth definitions and the ability to browse by usage, themes, and popularity, among other categories, as well as a random name generator, surname database, and how names are used in different countries.
BabyNames.com – Not nearly as thorough as Behind the Name, but it contains a much larger database of names. It also has an article of Tips for Writers. Most of them are pretty obvious, but sometimes you need to be reminded of the obvious, and the user comments are quite interesting as well.
“The Random Name Generator” – An interesting generator that allows you to set an obscurity factor based on U.S. census data.
Fantasy Name Generator – There are tons of random fantasy name generators out there, but few have a wide a scope as this one.
Motivations Deck – Motivation cards for a particular role-playing game, but these can be generally useful when putting together a new character for fiction as well.
GWW Character Questionnaires – Some good things to think about when creating or fleshing out a character.
The Universal Mary Sue Litmus Test – Use this very cautiously. It is largely based on the personal opinion of the person who wrote it, and is by no means an indicator of a “good” character. However, it can be a very interesting tool to reflect on.
Worldbuilding and Setting
The Language Construction Kit – Even after constructing several languages to various degrees, I refer back here when starting a new one. I also browse the Wikipedia pages on various foreign languages to gain inspiration.
Miscellaneous Writing Sites
LibreOffice – A free, open-source office suite.
Seventh Sanctum – This site is chock full of random generators. Most of them are pretty silly, but there are some cool ones and it provides good inspiration.
Tribal Pages – A free site that allows you to create family trees, excellent for the organization of characters.
The Speech Accent Archive – A cool, and quite thorough, reference for accents.
Writing Excuses – A great, long-running podcast for fiction writers, especially those of science fiction and fantasy.
Uncle Orson’s Writing Class – Articles by popular science-fiction writer Orson Scott Card.