Guide to Grammar and Writing
Award-winning site from Capital Community College, Hartford. Includes detailed tutorials on grammar and writing at the sentence, paragraph, and essay level; PowerPoint presentations and interactive quizzes; extensive links to writing-related sites; and an "Ask Grammar" feature where you can get answers to questions on grammar.
http://webster.commnet.edu/grammar/index.htm

English as a Second Language Site
This site by Rong-Chang Li contains general information on writing and grammar as well as an extensive list of links relating specifically to Business English.
http://www.rong-chang.com/

Purdue University Online Writing Lab (OWL)
This excellent site includes instructional handouts, extensive links to writing-related sites, help for ESL students, professional writing resources, and much more.
http://owl.english.purdue.edu/

Online Technical Writing
Austin Community College
This comprehensive site includes information on many of the topics discussed in your textbook, including document design, business correspondence and resumes, proposals, instructions, oral presentations, the writing process, audience analysis, and team writing.
http://www.io.com/~hcexres/tcm1603/acchtml/acctoc.html

Writing User-Friendly Documents
The Plain Language Action and Information Network
A guide to clear writing, originally produced by the National Partnership for Reinventing Government.
http://www.plainlanguage.gov/handbook/index.htm