Punctuation lapses into a comma | Larry Parsons, MontereyHerald.com :

Comma misuse can be deadly serious.

Sipping my second coffee, my thoughts wandered from appositives and comma splices to my personal failings in punctuation relationships. I confess I have been a cad in mistreating the lovely dash, or L.D., for most of my life. She didn't deserve this boorish behavior. She was always straight with me.

You might get a sense of it from that introduction, but Parsons writes a enjoyable column here. I won't attempt to summarize it. I'll just encourage you to read it.

For more serious resources about punctuation, check out the Punctuation section of Garbl's Onine Grammar Guides. You also can check the punctuation entries at Garbl's Editorial Style Manual.