For writing guides on persuasive or argumentative styles of writing, see the OWL Writing Center web site from Purdue University:
Arranged in alphabetical format, this website provides a list of commonly misused phrases and explains the correct usage. It also includes explanations of the proper useage of parts of speech.
These OWL resources will help you with the writing process: pre-writing (invention), developing research questions and outlines, composing thesis statements, and proofreading.
The Guide to Grammar and Writing is sponsored by the Capital Community College Foundation.