You can order today (at least, according to Bezos - so far, the links are not live at Amazon; I'll update the post when they are) and it will ship October 1. The ad-supported non-Touch Kindle will be dropping in price to $69 - that price is now live and the no-ads Kindle has dropped to $89 (out of stock until Sept 8).
There are already Accessories and Warranties available and a helpful reader has pointed out what looks like a pricing error on the new CaseCrown Kindle Paperwhite Flip Covers, as they are currently only $3.23 on pre-order! I've ordered a couple (but these dropped to "shipping soon" almost immediately, even with a Sept 30 ship date, so don't expect to be able to cancel the order).
The new, faster Kindle Fire will be lower in price, as well: $159 and both a 7" Kindle Fire HD and 8.9" Kindle Fire HD, with 1920 x 1200 display — 254 ppi and only 20 oz in weight. The 7" model will have double the memory of the original Fire and a faster processor. They've also added a polarizing filter layer on both models, so that there should be less glare on the screen. On the larger, HD Fire, you'll get dual, stereo speakers and Dolby Digital Plus. The WiFi has been upgraded to 5GHZ and there are two antennas, which should improve WiFi connectivity if you are farther from the hotspot. As for storage, the HD will start with a 16GB version and will have BlueTooth support and HDMI out! Pricing for the Fire HD: 7", 16 GB $199 / 32GB $249, 8.9" 16GB $299; shipping Nov 20th on the larger tablet and Sept 14 for the lower priced model. That's only a $40 difference vs. the non-HD Fire, so I'm going to recommend that you only consider the HD edition.
For those who want 4G coverage, there is a $499 Kindle Fire HD with 4G LTE wireless, that has an Amazon designed modem, 32GB storage and the 8.9" screen (and a second model with 64GB for $599). It looks like it will connect with AT&T. The data plan is $49.99 per year, with 250MB a month, 200GB of cloud storage and a $10 Amazon credit. That's not much bandwidth, but is enough to play in the Kindle store and check your email regularly, when you don't have WiFi access. There are probably upgraded options on plans, for those willing to pay for it, but nothing announced at the conference.
They've also added Whispersync for Voice, so you can sync your Audible listening to reading the ebook on another device. So, listen in your car, then sync at home and read the ebook later. They also have added Immersion Reading that lets you read the book at the same time you listen to the audiobook.
Also, WhisperSync for Game (ooh!), X-Ray for Movies, new Email support (including Exchange support for business users), a custom Facebook App, Skype (so, yes a camera and microphone are now included), Time Limits for Kids (I've been seeing people ask for this lately, in the Kindle forums), multiple profiles (yay!) for family members (or letting someone look at your tablet) and a different color on the background (light blue) so you can tell if your kids are using their FreeTime profile. For reading, X-Ray for books will show you both Wiki entries and YouTube videos. There should be some new magazines offerings, also.
I am seeing a few Kindle Fire HD covers, also, although only for the 7" model, so far (they are also discounted as pre-orders, for those that want to get a jump on things).
If you put in an order now, you'll be in line for delivery - I expect there to be a backlog before Christmas and there may or may not be enough that those who opt for SuperSaver shipping will get theirs in the first batch. In the past, Amazon has bumped all the people who pay for overnight shipping (usually a $3.99 charge for Prime members) to the front of the list, followed by those who order with 2nd day shipping and those with SuperSave shipping end up nearer the end of the pack. Also, if past years are any indication, these are going to be some of the hottest gifts under the tree at Christmas (especially by parents who are tired of trying to get their kids to quit using the iPads for hours each day).