I saw that no one posted under the thread "Houseboat Rental" so I figured I'd get the discussion going.
If you are looking to charter a houseboat, I'd suggest looking at Yachtico.com. They have over 15,000 charter yachts around the world and 590 of those are houseboats. Here is the link to all 590 Houseboat Rentals Worldwide. I suggest you take a look and compare prices with other rentals.
Has anyone chartered with Yachtico before? From the research I've done, I've only read good reviews from people.