BBC vs. Wikipedia
You can probably tell that I read the BBC headlines that come with Firefox. Batteries included. Punctuation at a slight extra cost. Actually what I'm trying to say is that if you want to teach how people NOT to use punctuation, look at the horrible example that BBC puts out many times a day. The English have some bad habits in that respect, and us Yanks have some of our own. That said, there is a place to find good puctuation: Wikipedia. I was doing the wiki dance somewhat early on, and I recall the community working out what would be the international standards for English on Wikipedia. Very good work.

Of course you can find bad work there too. And when you do, fix it!