Amazing BEN FRANKLIN Inventions: You Can Build Yourself . It is a great book which gives some background on how and why Benjamin Franklin invented the items he did and then offers a wide variety of ideas to try out.
Our first adventure was making swim paddles because young Ben loved the water and swimming. He wanted to go faster so he invented both hand paddles and fins. Froggy has yet to test hers out because winter is not the best time for heading to the pool.