I remember someone posted a thread here not too long ago, saying BestBuy was selling the base MacBook Air for $899, on sale until the end of today, if I remember correctly.
MacMall also has cheaper prices, and in many states does not have sales tax. While they are an "authorized Apple reseller", I bought my MacBook Air from the actual Apple Store just for the peace of mind, because I had heard their customer service was not up to standards.
Hope that helps!