Try MacMall. They seem to have the lowest prices as of right now - even lower than Amazon. Hopefully you're in a state where sales tax won't apply to your purchase. I, too, am in the market for an MBA and have been keeping an eye on the prices for a few months and I've noticed that MacMall has the best deals.
The one I want (base 13-inch model) has been on sale at MacMall for $1197 on several occasions and, unfortunately, I couldn't buy then, or a couple weeks ago when Best Buy had their $200 off sale. So, now that Christmas shopping is underway, I expect them to have sales once again, in order to boost numbers. I will definitely be buying one within the next three weeks, so I'm keeping my fingers crossed.