Amazon sell remanufactured models of the Roomba and books on reprogramming them.
Hacking Roomba: ExtremeTech, Tod E. Kurt, 2006:
A gizmo as cool as Roomba just begs to be hacked. Now, with this book and the official ROI specification furnished by iRobot®, you can become the robotic engineer you've always dreamed of being. Build a Bluetooth interface for your Roomba. Turn it into an artist. Install Linux on it and give it a new brain. Some hacks are functional, others are purely fun. ...The new LEGO Mindstorms NXT robot kit with a 32 bit processor is also available. These are popular at universities as well as for hobbyists.
LEGO Mindstorms NXT robot kit:
Set includes: NXT programmable LEGO brick, ultrasonic sensor, sound sensor, light sensor, touch sensor, 3 interactive servo motors, USB cable, 7 6-wire cables, building instructions, user guide, Quickstart guide, easy to use software and test panel. 6 AA batteries not included.LEGO MINDSTORMS NXT Hacker's Guide, Dave Prochnow, 2006:
• Your First Robot • Stupid RCX Tricks • Save Your RIS • As Smart as a Brick • MOVE IT! With Servo Motors • Hmm, I Sense Something • Yes, But I Don't Know How to Program • Testing, Testing; Oh, Trouble Shoot • Katherine's Best Hacking Projects • Katherine's Design Fun House • NXT Programming Language Guide • NXT Elements • NXT Resources
See also: Robot store, with kits, books and videos.