Engadget posted two screenshots, first is a shelf tag spotted this weekend at a Best Buy in Houston: White iPhone 4, AT&T, $599.99 off contract (the same price as the black). And in case you're wondering, the QR code link is dead at the moment.
Secondly, a Canadian version of Radio Shack is also making room. See for yourself:
[tags]white iPhone 4,best buy,radio shack,apple,canada,white iphone,[/tags]