I went 3 years ago. Wasnt in Orlando for too long, 2/3 days i think, as we went to Tampa and Clearwater.
Not too far from us is all the Disney parks, Universal, Busch Gardens, Epcott.
Also there is the Sea World place, a water park. Thats all i can remember.
Like someone else said Disney and if you like swimming the beaches are really nice.
If you're into night life head down to Miami where they have quite a few nice clubs.
Went there not so long ago (around a year or two) and although it sounds ghey, defo check out the 'strip' - not sure if it's actually called that or if that is just a tourism thingy for it. Either way it features a long road of bars, clubs, restaurants, fairs etc..