I hear Pumpkin Patch has some, and there is a sale now. We'll see, I'm going tomorrow... Also, H&M has a section in the back between kids clothes and bras. But, right now their regular styles are somewhat tent-like, so I can't tell much of a difference between their regular stuff and maternity. Sizes for the maternity clothes are a bit small though, I'm only 5 months and their Large size was a bit snug already (I'm not that big!)
Also, you can shop at the Qatari-style clothing stores (like on the back isles of City Center). The styles are less form-fitting than the western styles so I have found those are good maternity clothes.
Oh, and I just went shopping at the Next sale, and found some nice tops there that work for maternity clothes.