You may find these links useful for your assignments in writing classes.
General Grammar Sites of Interest
Online Writing Centers and Writing Labs
Florida State University's Writing Center
University of Georgia Online Writing Center
Purdue University's Online Writing Lab (OWL)
The University of West Florida's OWLReference Guides
Dictionary.com
Thesaurus.com
Modern Language Association Style FAQ
Citing Electronic Sources
Bartlett's Quotations Online
The Columbia Guide to Online Style
Strunk and White's The Elements of Style
Landmark Citation Machine