I really, really liked the Healesville Sanctuary. It's an Australian native animal zoo, set in bushland. It's entertaining and educational. Lot's of walking and getting close up to the animals. You can get up close and personal for an extra fee, but we didn't. It was still cool.
There's extinction fighting superheroes, and if you find yourself perched on the loo at any time, you'll hear a voice over from someone called Crap Man, informing you about the benefits of using recycled dunny paper. They really push that here.
The bird show is a must see. There's Kevin the talking bird, a Corella, and loads of other fabulous birds who do cool stuff.