The iRobot Roomba 510 vacuum cleaning robot is just $159.99 at Buy.com. The Roomba machine vacuums your entire house on command, calculating the optimal cleaning path, and it returns itself to its charger. The 510 model is even more advanced, featuring improved performance, reliability and durability. Compare this price to $250 at Amazon. Shipping is free, there's no sales tax (except CA, MA, MD, TN), and new Google Checkout users can get a $10 discount for signing up.