You've got two big ones to choose from.
Close to Downtown Disney there is the Orlando Premium Outlets. This is designed in kind of a triangle, with a food court at the centre, is well shaded with canopies over the walkways, and has a very wide range of all the shops you'd expect at a Premium Outlets - Timberland, Nike, Clarks, Banana Republic, Brooks Brothers etc etc
The other major outlet spot is up at the very top of I-Drive - a much longer drive (or taxi ride) from Disney. This used to be called Belz, but is now rebranded and rebuilt and called Prime Outlets. When I went last Christmas it was not fully open yet, but it was clearly going to be a bigger place than the Premium Outlets once it was all open. It had a huge choice of stores too, but I didn't like that the walkways we saw didn't have any shade, which I need! It's possible they've added that since I was there.
They both have websites where I think you can check which stores each one has before you go, so if there is something particular you're looking for that might help you!
They're both great choices. Happy shopping!
Miranda