Scratch

Well, there's any of the Sample projects that come with Scratch.  Just click on File-Open and then on the Examples button.  Where you go from there depends on what kind of project you think people would find interesting.  I like the Interactive Art ones myself.

I'm going to move this to Project Ideas as it seems to be a good fit for that category 

If you're making a scratch club at school, you could always come up with a character that seems likable, and use him or her as your mascot. Once you have them drawn up, perhaps you could put together a short and simple animation of your character explaining the club. Throw in a thing or two about why they should join it, and end it.