The Multi-Bot project for NXT 2.0 from nxtprograms.com is a robot vehicle that can take a number of different forms, including taking on several different modular attachments that can be used individually or combined in various ways, all using a single NXT 2.0 (8547) kit, or equivalent/replacement parts from other NXT/Technic kits.
Multi-Bot was designed to be a flexible "teaching robot" of sorts for NXT 2.0, especially as an aid to learning NXT-G programming, as you can use it to do a lot of classic robot vehicle tasks and expand it to do your own tasks. Home users of NXT 2.0 might find it a good way to learn about the basics of robotic vehicles, and especially in conjunction with the CD (see below) as a good way to learn a lot of NXT-G programming. FLL teams that have the 2.0 retail kit (8547) or equivalent parts and software might also be interested in using it as an educational tool before the regular FLL season starts or at the beginning of the season.
Building instructions for Multi-Bot, its variations, and several different attachments using all the standard NXT 2.0 sensor types are available on the web site. In addition, over 70 ready-to-run and fully commented NXT-G programs for Multi-Bot are available on the CD LEGO MINDSTORMS NXT 2.0 by Example. The programs range in complexity from beginner to advanced and cover different ways to control the motors, use the sensors, and more. The program descriptions are also included on the web site. Users or teams with some programming experience may want to see if they can develop similar programs on their own given the descriptions. Or if you like learning by example, get the CD and study the programs in each section (which are arranged in increasing difficulty) to learn NXT-G programming with ready-to-run examples all using Multi-Bot. Since you can quickly reconfigure Multi-Bot for the different tasks, you can cover a lot of programming topics without a lot of rebuilding.
Here is a video showing the included attachments for Multi-Bot and video clips showing tasks from selected programs on the CD: