I'm not sure wher Bighoss has been shopping, but pretty much every Walmart I know of was and still is selling Colt 6920's for $1097. The 6920 is Colt's basic civilain legal version of the M4 they build for military and police. It's built to the same standards and with the same quality, and it's a great deal for what you get.
But back to the original question, there are so many different companies out there producing AR's and all with varriying levels of quality and pricing creating a such a list is a very difficult task. As another member posted, the best place to start is the manufacturer's websites which should include the MSRP's for their various offerings. Take a look at what's out there, take a good detailed look at what you will be using the gun for, do some research on quality and pricing and then purchase accordinginly.
"Si vis pacem, para bellum" - If you want peace, prepare for war.