From Will's blog, Slade's Language Teaching Blog, I found two precious sites for writing reference resources which are greatly helpful for both teachers and students.
Undergraduate Writing Center of the University of Texas at Austin developed an online version of the consulting services of the center for those students who have to work on writing on their own without visiting the UWC. The online writing center is called Virgil, and unlike many other writing help sites which sometimes add more confusion to visitors, Virgil is very neatly organized according to writing stages and easy to find a resource one is looking for. Anyone who needs tips for writing can refer to this site for English grammar, writing format, citation, punctuation, and many more. The site provides "Writing Handouts" both in the HTML and PDF versions, which teachers can print out for their students. Looking around this site, I felt like I've got a private writing tutor.
Guide to Grammar and Writing provided by the Capital Community College Foundation is also another useful site. It might take a while to get familiar with this site at first, but once done, it provides an enormous amount of references for English grammar and composition. Principles of Composition, as a part of the site, is specifically focused on composition. One of the strengths of this site is that they provide ample explanations and examples for each grammatical point or writing principle. I believe this site would be a great reference site especially for teachers.
