Try steel--it's supposed to be a smoother ride (with the right quality tubing) for about the same price as aluminum. Jamis makes some nice steel road bikes (I'm looking at a Quest Femme) at reasonable prices. There's also Surly.

As far as aluminum...try Specialized, Giant and Cannondale as well as Trek. Giant may not work for you depending on your proportions (they tend to have long top tubes), but they make nice bikes for the price. Cannondale's "thing" is supposed to be aluminum. There's some discussion in the "general" section of the forum right now about aluminum's vibration problems and tubing quality/frame geometry. If you're willing to take a crack at a more aggressive position, the CAAD10 is supposed (according to shop, Bicycling magazine and Cannondale representative ) to be about as nice a ride as its carbon equivalent for much less money.