Kangaroos at Columbus and Cincinatti Zoos, a bunch of good Walk-through aviaries, the deer forest at Southwick's Zoo, that's what I can think of off the top of my head.
That whole zoo is perilous for bugs though. I haven't been to Southwick's in a number of years, but one of the things I remember about it is the prevalence of bees, especially around the dining areas.
A couple of my favorite walkthrough Australian exhibits would be Kangaroo Kickabout in Nashville with a large, grassy, hilly habitat for red kangaroos and perches for cockatoos - plus the Aussie theming and details are nice touches (and the excellent pair of cassowary exhibits nearby add to the experience); and Walkabout Creek in Racine - a lush, scenic loop with kangaroos, wallabies, emus, and I believe wallaroos. Other unique walkthrough exhibits I've seen include: - White-tailed deer habitat in Kids Kingdom (Pittsburgh Zoo & PPG Aquarium) - Red ruffed lemur habitat in Expedition Madagascar (Omaha's Henry Doorly Zoo & Aquarium) - Penguin & Puffin Coast (Saint Louis Zoo) - The African Aviary in Flights of Fancy (Indianapolis Zoo), due to the surprise addition of hyrax
I forgot about Penguin and Puffin Coast- that's definitely a contender for the country's best Walk-through habitat, or at least the most unique. I'm also glad that there's an AZA zoo with a Lemur Walk-through, I've known this is possible, but didn't know of any AZA zoos with one of these exhibits. Personally, I'm a big fan of walkthrough habitats and would like to see them more often, when safety allows of course. Ideally I believe every zoo should have at least one walk-through or interactive Exhibit, guests seem to really respond well to these kinds of interactions with animals- whether it be birds, kangaroos, goats, or anything else.
They do have a Lemur Walk at the San Diego Zoo Safari Park with Ring Tailed Lemurs that can hop right in front of you
One not mentioned yet is Walkabout Australia at the San Diego Zoo Safari Park. The walkthrough section is the Marsupial Walkway that is separated from the rest of Walkabout Australia. There are western grey kangaroos, red necked wallabies, magpie geese, radjah shelducks. The kangaroos are more curious of the whole bunch and they have right of way even on the walkway