I'd collected a bunch of Angry Birds stuff (posters, postcards, stickers, etc) for some time and I thought they would make great giveaways at an Angry Birds program. I found a treasure trove of printables at this awesome website and printed out some of the boxes with handles. I cut off the handles while making them so they could just be cube boxes. The TNT boxes came from this website and a good tutorial for the popsicle stick catapult can be found at this cool site.
I found the little bouncy Angry Birds balls shown on the catapult site, but they were really expensive. Oriental Trading has some Crazy Bird Molded Bouncing Balls that were cheap and fit perfect in the bottle cap of the catapult.
Here are some images of the final products, and you can see some really awesome kid lined up his Crazy Bird balls to take a turn on the catapult.