Pooh and friends can be found in every park! At Magic Kingdom, there are in the ToonTown Hall of Fame, which is the gift store between Minnie's and Mickey's Houses. When entering, go to the right, and there are lines there and one leads to Pooh and friends. We met Pooh, Tigger, Eeyore, and Piglet there in November. They meet there for most of the day.
At MGM, they meet in front of the Big Hat, usually in the late mornings/early afternoons, like 11:00ish to 2:00ish, on half-hour intrevals. Usually two of the gang are out.
Like DisneyPHD said, at Animal Kingdom, Pooh and friends meet on a Dock on the way to Dinoland, right before the bridge. I seen Eeyore, Pooh, and Tigger there on every trip.
At Epcot, they can be found in the back of the Toy Store in England, off the main sidewalk. I also seen them in the courtyard area outside the Toy Store, and I seen them on the Epcot Bus, too.
Fortunately, Pooh and friends are pretty easy to find! Pooh, Tigger and Eeyore are most common. Piglet is somewhat rarer, but we usually see him somewhere on each trip. The really rare one is Rabbit, you would be really lucky to find him!
Have fun!!!