If you are interested in the programming side you can start with something like Lego MINDSTORMS. If you are more interested in the electronics side you may want to check out some of the kits on Parallax and The Robot Store.
You will find a mix of languages and platforms so really pick your favorite languages and find something in your price range. Robotics can be very fun (and very time consuming.)
BTW, you can make a pretty cool robot with just an RC car and a BASIC Stamp. And if you have a parallel port on your computer you can interface your computer to the RC car for even more power.