Note: Generally speaking, these writing centers make it clear that they are NOT proofreading services; they are available to help you improve your writing. If you contact them for help, expect to do some serious writing and revising. Many of the centers also offer online handouts and other services. If one OWL doesn't meet your writing needs, try another.
Dakota State University's OWL
http://www.departments.dsu.edu/owl/
The Online Writery
http://www.missouri.edu/~writery/
SUNY@Albany OWL
http://www.albany.edu/writing/
University of Minnesota Center
Includes e-mail consultations and a chatroom for "live"
tutoring.
http://www.owc.umn.edu/
WSU's Online Writing Lab
http://owl.wsu.edu/
Visit USD's English Dept. home page.