Punctuation

Joys of Punctuation
Explains when to use commas, semicolons, dashes and hyphens, with light-hearted examples of correct and incorrect usage.
http://www.engl.niu.edu/comskills/students/editing/Joy.html

Punctuation
Describes common difficulties and how to work out the correct usage, as well as taking account of international differences.
http://www.stage-door.org/stampact/punc.html

Punctuation
A detailed look at how to use punctuation effectively and correctly. Discusses each mark in turn, with a quiz in each section to test understanding.
http://www.uottawa.ca/academic/arts/writcent/hypergrammar/punct.html

Punctuation Reminders
A list of the most common errors, with sentences indicating correct usage.
http://www.virtualsalt.com/punctu8.htm

Punctuation Tips
Features a list of commonly used and misused punctuation marks, with examples.
http://www.lrcom.com/tips/punctuation.htm

Quotations and Correct Punctuation
Explains and illustrates the rules which apply to quoted material, including where to place colons and commas.
http://plato.acadiau.ca/dagora/tutorial/qpunct.html