I was asked by my agency, InterTrend Communications (an Asian-American ad shop) to host a Twitter101 lunch and learn session. This is a pretty basic overview of Twitter that led into a "hands-on" demo/walk-thru. There's certainly much better and more in-depth decks out there by much smarter folks that myself. I hope this gives you a springboard to creating your own Twitter101 preso. thanks.
Clipping is a handy way to collect important slides you want to go back to later.