I will start with the fact I've lived in Florida for much of my life and have seen manatees in the wild many times. They are facinating, adorable creatures. For those of you who haven't seen them in the wild and don't want to go to the Lowry Park Zoo (where they have a great manatee exhibit and hospital), the Teco Viewing Center is an alternative.
The best part of the attraction is that it is free (thank you Teco). However, you have to time your visit to when it is cold. And don't base your decision to go entirely on the web-cams at the Teco website, because those cameras are not very close to the boardwalks that people are allowed on. We went toward the later part of the season. There were lots of manatees on the webcam, but when we got to the boardwalks all you saw was manatees breaking the surface of the water almost a full football field away. None were close to the boardwalk. This was a bit disappointing to drive as far as we did from North Tampa to see very little.