The Moto 360 is supposed to go on sale in the U.S. at noon ET September 5th (that's tomorrow if you're reading this as it's posted). However, it appears that you can add the two available variants to your cart and checkout with the right links, which we are happy to provide.
If you want the silver Moto 360 with a gray leather band use this link. For the black 360 with a black band, you want this one. Since both have leather bands, the price is $249.99 plus tax. You won't get any customization options, though. Even trying to change the band color in the cart won't work. It's possible Motorola only has very specific SKUs ready to go.
It looks like orders are going through and confirmations are being emailed. It's still possible Motorola will cancel these orders, but everything looks legit right now. The Motorola site lists the arrival date as September 10th, but that might just be a place holder.