Many good handouts on writing are available at the Online Writing Labs at colleges and universities worldwide.  You can find handouts on rules, writing advice in checklist or essay form, and model essays or paragraphs.  A limited list of recommended sites follows:

George Mason University Writing Center

Community College of Southern Nevada Online Writing Center

Writing Center Online Guide, Lynchburg College

The Nesbitt-Johnston Writing Center at Hamilton College

Temple University Writing Center

The Writing Center at Rensselaer Polytechnic Institute 

The Writing Center at the University of North Carolina at Chapel Hill

Texas A&M University Writing Center