The Internet Controlled RC Car allows you to remotely drive around a small rc car from wherever you may be and see where it is going. This is fun because you can remote explore whatever space you leave it in, or hand over the keys - so to speak - and allow someone to drive around your space. This is also a great building block for a telepresence robot.
This project is also a great beginner project for someone who has made a few simple things and is looking to get slightly deeper into the world of microcontrollers. It starts to incorporate more advanced skills like circuit building and networking, but is not dauntingly complex.