You can't get to the Disney parks, but you can get to Island Of Adventure, Universal Studios, Wet & Wild, Sea World & Discovery Cove, The Titanic Exhibition, Ripleys, and Wonderworks. Oh yes, and the super new waterpark attraction opening Mar 2008...."Aquatica".
However, if you want to get to the Disney Parks a bit more cheaply, assuming your hotel does not run a shuttle bus service ( and many of them do); go to the furthest point on the I drive south, the Premium Outlet, and take a taxi from there, as the Disney parks are quite a way from central Orlando.
The I-ride trolley is cheap and really easy to use.