Shedd Aquarium was a good time, although expensive. Jane is under 3 so was free, which made the sticker price a little less shocking. We went early to beat the crowds, and for the first hour or so we didn't have hordes of people around us. After we watched our 10:30 dolphin show though it started crowding up, and when we left by 1 pm it was impossible to see the exhibits because of all the humanity.
Jane loved everything, especially the iPads they had at most of the tanks to give more information about the fish and sea creatures inside. She also loved the 4-D movie -- 15 minutes of Ice Age: Dawn of the Dinosaurs. It was scarier than I expected! But I do love Ray Romano's voice though.
My favorite were the jellies. Even though they're invasive and horrible they are beautiful to look at in a tank under those pretty pretty lights!