Nvidia RTX 3080 sales will go live on September 17 at 6 a.m.
Having said that, there is no harm in trying. It also doesn't hurt to bookmark a few of these retailers in case the GPU sells out in milliseconds - you can re-register to see when the stock inevitably refreshes. Remember this: Nvidia Founder's Edition will cost $ 699, and AIB Partners will cost around $ 20- $ 150 more (and even more if you factor in the turbo-charged versions with cooling packs in the air. water preinstalled). If you're starting to see the Nvidia RTX 3080 selling for over $ 900, you're probably looking for resellers. I would advise being patient if you can't find an RTX 3080 around the MSRP - with AMD's Big Navi on the way and Nvidia's 3070 launching in October, you better not throw your money in the wind in desperation.
As for retailers, Amazon, Best Buy, and Newegg have their pages for the 3080. If you want a Founder's Edition, you'll want to look to Best Buy and the Nvidia pages themselves, but each has a selection of AIB partner boards. to choose from if you don't care about the FE Card. Other retailers, like Photo B&H will also have a few cards in stock if you want to keep your options open (however, Fry's Electronics fans will want to look elsewhere: they still have the RTX 20 series listed as "coming soon"). You can't book one, so you'll have to get up early (at least on the West Coast of the United States) if you want to catch one.
My advice: open or verify your account with everyone, and make sure not only your address is correct, but also your payment option. Everyone's web pages will likely be under a lot of pressure once the doors open, so the less you have to enter during checkout, the better. Having your information pre-populated could literally be the difference between grabbing an Nvidia RTX 3080 at launch or having to wait for a replenishment. I'm going to be in the trenches with everyone, so good luck - we'll need it.