Someone mentioned bikesdirect. I've never bought anything from them, but the prices sure are enticing! The comments I've read seem to suggest that people are usually happy with the purchase, and when things go wrong the customer service is good. For your purposes, I'd say go to road bikes, and then the sub group cyclocross. Here's a nice looking budget model I noticed with an aluminum frame and steel fork:
http://www.bikesdirect.com/products/...liberty_cx.htm
By the way, I wouldn't worry too much if you find a bike you like without rack mounts. It's easy enough to mount a rack with little p-clamps, and it works fine.