Basic Line Following
This is a great contest for beginners to try to tackle. Its just a bit harder than basic table top and probably about on par with Advanced Table Top.
Past and Present Basic Line Following Rulesets:
One of the great things about this contest is that you'll find about a bazillion examples of line following robots on the web. Dave Cook's Sandwich robot is a great first robot to build from scratch. There is also Mike Davey's CBABot that comes in kit form with everything you need to get going.