In print:

Diana Hacker. A Writer's Reference. 5th ed. Boston: Bedford/St. Martin's, 2003. https://library.villanova.edu/Find/Record/619448

William Zinsser. On Writing Well: An Informal Guide to Writing Nonfiction. New York: Harper & Row, 1980. https://library.villanova.edu/Find/Record/7630

William Strunk and E. B. White. The Elements of Style. New York: Penguin Press, 2005. https://library.villanova.edu/Find/Record/697043

Gerald Graff. They Say, I Say: The Moves that Matter in Academic Writing. New York: W.W. Norton & Co., 2010. https://library.villanova.edu/Find/Record/1242329

Jan A. Pechenik. A Short Guide to Writing About Biology Boston: Pearson, 2013. https://library.villanova.edu/Find/Record/1437062

Online:

Research as a Second Language. The blog of philosopher and academic writing coach Thomas Basbøll. http://secondlanguage.blogspot.com/

The Mumford Method. A procedure for producing clear, well-structured writing, developed by philosopher Stephen Mumford. 
https://sites.google.com/site/stephendmumford/the-mumford-method

Explorations of Style. The blog of philosophy and academic writing instructor Rachel Cayley. http://explorationsofstyle.com/

The Writing Life. An archive of John McPhee’s essays for The New Yorker. http://www.newyorker.com/magazine/the-writing-life

Lingua Franca. A blog about academic writing at The Chronicle of Higher Education. http://chronicle.com/blogs/linguafranca/