The Georgia Aquarium can't be beat, IMO. We went there in September as an early birthday celebration, and it was absolutely AMAZING. The Whale Shark Tank was massive, of course, and there were tons of different viewing windows. The best window, though, was the floor-to-ceiling one. You feel like you're actually IN the tank. They have carpeted steps set up in front of it, so you could sit there all day if you'd like... There are four Whale Sharks and they frequently swim in front of the windows, along with huge Groupers, Humpback Wrasses, Sharks and Stingrays.
Their Reef exhibit was breath-taking! I was really excited to be able to see large, fat Moorish Idols swimming around. Talk about Heaven! I even spotted a cute Valentini Puffer and told Nick, "Look, there's Diddy!"
I want to say that 40% of their corals are now real, and they're already proprogating their own with donations that were made. The tank looks great, and I am sooo jealous
I fell in love with the Beluga Whales. They're so beautiful and graceful. They had a very interesting presentation, as well; facts and such... They were working on the Penguin exhibit, but we got to see some cute Sea Otters (man, those teeth are massive!) and watch them being fed.
The other exhibits were pretty cool, but nothing compared to the Reef/Beluga Whales/Whale Sharks... They had an anemone touch-tank, a Bonnethead Shark & Stingray touch-tank, and a Shrimp touch-tank. (The Shrimp creeped the heck out me!)
The best part of the whole day, though, was probably the Behind the Scenes Tour. Definitely well worth it! You get to walk on the catwalk above the Whale Shark Tank, see all of the machinery (skimmers galore!) their nursery (they were keeping baby Bamboo Sharks and Pearly Jawfish when we went)their Coral Propogation tank, their state-of-the-art kitchen and medical center, as well as some cool tanks that are up in offices and such (225 Reef; Seahorse tank; Dart Frog tank, etc.)
...I'm sure I'm forgetting something, but either way, it's a must-do when you're there
Their gift-shops are pretty neat, and you can bring home some cool souveniers. Food is a little pricey but that's to be expected... (One tuna sandwich cost me $7.50. It was pretty big, though.)
All-in-all, I highly recommend the Georgia Aquarium. You'll want to go back every weekend!