Everybody's already pretty much named it for you. Unfortunately, Orlando isn't the best city in the world for mall shopping.
Festival Bay is the new one near Belz with the Ron Jon's. It's only about 20% full at the moment, but will eventually be a great mall. (No outlet stores.)
The Florida Mall is HUGE, but doesn't really have any excitingly different stores. If you're looking for regular mall stores, you'll find them all there, but be aware that some stores have jacked up the prices from their normal retail.
The Mall At Millenia has a great Macy's, but is fairly useless beyond that, unless you have a really really amazingly large shopping budget. All of the stores are high-end, and incredibly expensive. What I've been hearing lately is that it's not doing very well, and I'd believe it -- I don't know anybody local who shops there regularly.
The Premium Outlets on I-Drive next to the new Dixie Stampede are WONDERFUL. There's a good, diverse selection of stores, and you can usually find a few really great bargains. (Premium Outlets is actually a chain. If you've been to any others, you know pretty much what to expect.)
There is a Mills mall in Florida, but according to MapQuest it's about 3 hours away, darn it! If you're headed to Miami it would be worth routing your trip to pass it, but it's a heck of a schlep from here.
Man, I miss good malls, lol.