Well the major taks I get my robot to do is go to the kitchen and return to where ever I am with a trailor and a drink in it! He has a tiny sound recorder/player so I record something like "A Beer please" and then let him run. He goes to the kitchen then stops and plays what I record. My wife deposits the drink in the trailor and pushes a button and he returns to me with my drink.
But I'm sure there are other tasks like hauling a digital camera for survaliance or even one of those cool wireless video cameras. Take a picture or get live video feed. Send him out under the car to see whats leaking. Or make him a waterproof ROV to clean the pool's suction grill. Spy on the neighbors.
Some other ideas: give him a pincil and make him draw, or better yet a wireless dermel and let him engrave something!
Or you could always go the Aibo route and make him a pet of sorts.
Make him control the household thermostat! Or water heater. He could turn things off when there is no one in the house.