I'm a teacher too.
All of these resources are simple and quick to download. They can be stored on a flashdrive, attached to a keyring and then they live in your pocket as easy and as ready to use as a hanky when a sneeze is coming on.
Try the Nonsense Rhymes Crosswords. If you like Dr Seuss, you'll love these (and so will your students). The World News Crossword is published every Sunday evening. It's prefect for prompting discussion about current events.
A powerpoint presentation covering the Market Failure topic, including an explanation of market failure and detailed graphs showing the effect of externalities.
The presentation is in MS Powerpoint format so it can be edited.