Herbie the Mousebot is a very straightforward but rewarding project to build. The mousebot comes in a package with the parts you need, and the assembly should not be difficult. The end project gives you a quick little robotic rodent that follows a light source. You can make it scamper about by shining a light and moving it directly in front of the little bot.
The video by Make shows the construction and some of the action afterwards. This would be a great project for an education opportunity or to just have some fun.