LEGO Mindstorms are incredible. It was teaching kids, students and grown-ups alike about programming long before devices like the Raspberry Pi mini-computer were even conceived. I stopped using them a while ago and while I wasn't looking, Mindstorms suddenly got amazing. Here's a bunch of robots working together to simulate a Las Vegas table game.
The new Mindstorms kits will let you add extra ports and functionality to the kit as you go, and you can also get instructions on how to build new kits via the Mindstorms app for your phone.