Walmart has started selling the iPhone 3G in selected stores. It's not not available on Walmart's web site. The price for the 16GB iPhone 3G (black and white) with 2-year contract on ATT is $297 and the 8GB is $197.
Walmart also sells accessories for the iPhone 3G, both in stores and online. The accessories range from cases from Speck, Contour to Bluetooth headsets from Jabra.