Amazon maintains a Kindle forum, for people who own a Kindle or are interested in getting one. If you're thinking of getting a Kindle, this is a great place to see what kind of complaints and praise Kindle owners express. Right not, though, it's full of people griping about changes in the Kindle 2—mostly the removal of the option to add and SD card, which is a loss of convenience, it's true, but I consider it to be balanced out by a better controller on the front of the Kindle. Not that I plan to trade in my Kindle 1. I am happy with it. But if I hadn't bought it (actually, my husband bought it as a gift), I would now be in line for a Kindle 2.
Coincidentally, Amazon is running another ABNA (Amazon Breakthrough Novel Award) contest, and they have a forum for that as well. The people on that forum are almost all entrants to the contest. One reason I like perusing it is I have found out a lot about how Amazon's Vine reviewer program works, and about how last year's contest was judged.
And finally, I was following the Authononmy forums a lot, but I find I just can't keep up with it all, so I haven't looked at it lately. The folks there are all writers who have posted on Authonomy hoping to attract the attention of HarperCollins (UK) and perhaps workshop their chapters a bit. Mostly they worry about who is doing well on the member-rated standing and if anyone has sold a book to HarperCollins. I've noticed a little overlap between Authonomy and ABNA, but none between either of them and the Kindle forums, which leads me to hope there are indeed readers out there who don't want to be writers!