The Purdue OWL (Online Writing Lab) offers over 200 free resources on writing, teaching writing, grammar and mechanics, English as a Second Language, and style guides.
Sponsored by Purdue University, this website is a great resource for people looking to teach and learn.
The "Grammar Tips" section will walk you through tons of pesky grammar rules, from whether or not you can end a sentence with a preposition to figuring out subject-verb agreement.
The blog also offers great advice about every part of the writing process from plotting to publishing, so be sure to check out the rest of the site's informative content.
Articles on Grammar Girl cover all sorts of topics (such as the weird history of oxymorons or the meaning of the phrase "in the doldrums") so you can visit to not only brush up on your grammar skills, but get a lesson in English language history.
The articles are snappy and fun to read, so you don't feel like you're engaging with boring material.
Of particular use on Lousy Writer are the cheat sheets, which help you understand tricky concepts like possessive nouns or homonyms.
These cheat sheets are great refreshers on difficult topics for English language speakers and English language learners alike.
Slick Write goes beyond spell checking to teach you the habits of effective writers. Bust your writer's block, and create new metaphors by playing the word association game.
To begin, type a word or phrase in the box below, and hit enter.