I have a couple that I love. One for front and back carries is my Baby Hak O-snap. It's longer in the body than an ergo but same sort of wearing/adjustment. I carried a 4yo around Ayers Rock and the Olgas. It's very comfy.
I also have a ring sling (a Sakura Bloom) whick is fab for quick side carries. Can carry my 3yo still quite easily.