Re: Baby carriers for wearing on the back?
I had a BabyHawk MT (sadly we lost it ) and we loved it. It worked well for back carries, though the long straps are a pain to deal with when out in public trying to get it all together. We recently got a NG Ergo and it's great! I'm really small framed and it's a little awkward at first, but it is so much more comfortable on my shoulders now that my son is 20+ pounds. My husband also really prefers the look of the Ergo.
FYI - You can get a used NG Ergo at www.myfavoritebabycarrier.com for $78 (includes shipping). We bought ours from this company. Fast shipping and hassle free place to order from