Grammar Resources:

Paul Brians' Common Errors in English Usage provides detailed and accurate explanations of the most common errors seen in writing. One of the treasures not to be missed is the section on non-errors. Feel free to use this site to disabuse persnickety friends and family of the notion that you should never split your infinitives or end a sentence with a preposition. There are times when doing so is entirely appropriate.

The Brief Penguin Handbook is an excellent source for grammar explanations and exercises for both native and non-native English speakers.

Plagiarism:

The Council of Writing Program Administrators' statement on plagiarism and the mutual responsibility that faculty and students share in avoiding it.

Writing Guides:

The Purdue University Online Writing Lab features more than 100 handouts on a variety of subjects from audience analysis to using semicolons correctly.

The Writer's Handbook is the University of Wisconsin's writing website. It contains information on writing research papers, science essays, application materials, and analytical literary papers.

Style Guides:

Kate McKinney Maddalena's excellent article on why it's important to use the first person in academic writing.  This essay is a chapter in Writing Spaces: Readings on Writing, Volume 1, a peer-reviewed open textbook series for the writing classroom, and is published through Parlor Press. The essay is available under the Creative Commons License.

References:

Merriam-Webster's Dictionary.  This on-line dictionary site finds definitions for input words and contains a very effective online thesaurus.

Technical Communication Resources:

Business Correspondence: Overview is a guide to the general format of business letters, discussing basic guidelines and basic business letter formats.