Today I learned: If you spin a hardboiled egg fast enough, it will stand up like a top. That's cool, but why does it happen?
In this Physics Girl video, Dianna Cowern demonstrates why spinning toys can exhibit surprising behaviors. As Cowern writes, "These behaviors all have to do with torque and angular momentum, like a bicycle wheel precessing around a rope due to gyroscopic behavior."
If you want to dig into the egg-spinning details some more, check out this 2006 paper (PDF link) entitled Can a spinning egg really jump?