One of the neat things I have seen people doing in this connected world is using the social networking sites to post questions such as "I am planning a trip to such and such area. Does anyone have any suggestions on where to go within the city, when to go, or what activities to do?"
Then people respond and suddenly there is are multiple items to put into your itinerary, and many times you have first or secondhand reviews as well as recent knowledge that you are getting, which is nice.
As far as having a full itinerary, my in-laws go on cruises and they love them for this factor as they love to be on the go. And with a cruise you are constantly on your way to a new destination and when you arrive at your destination you can fill your time with excursions (although these typically cost extra).