These colorful buses are free shuttle from WDW Village hotels to all theme parks at 1/2 hour interval. This is most convenient as one don't need to look for parking space & walk a long way from the entrance.
Mears transportation has shuttle service from the airport to all hotels. They can also take you from most hotels to different attractions. The price from the airport to area hotels is $24 one way, which is expensive, but generally cheaper than a cab. There's usually a wait, and since its a shuttle, you may have to make a few stops, so budget your time accordingly.
I flew into Orlando and stayed on-site at the the All-Sports Disney Hotel. We had to get a shuttle to the hotel - which took awhile even though we had reservations, but it was only a half an hour wait.
I used the Disney shuttle buses to go everywhere in Disney World - it comes with the room. We also caught a shuttle to Universal. I recommend using buses because it's cheaper.
The omnibus is fashioned after an old-timey double-decker bus with a spiral staircase in the back. It is one of several ways to get from the gate at Main Street USA to Cinderella's castle.
Orlando is provided by a bus system with routes called links, which is why the transit system is known as Lynx.
A free downrown shuttle loop called Lymmo uses natural gas powered buses.