KindleBoards
This is not a site just for writers. KindleBoards is an online community for those who love the Kindle, Amazon's dedicated e-reader device. That being said, if you are interested in promoting your work as a fiction writer, KindleBoards is a place you need to be, especially if you are selling your fiction in e-books for the Kindle.
Why do I suggest this? Because there is a growing number of traditionally-published authors as well as self-published indie authors who hang out regularly at KindleBoards, especially in the Writers' Cafe forum. Here you can catch some advice from long-time pros and up-and-comers, as well as pick up some news concerning writing and publishing.
If you just want to talk books, you can always check out The Book Corner. Or maybe you have a Kindle, in which case you might want to look into the Kindle Accessories forum, or the Let's Talk Kindle! forum. There are also Book Klubs, Reviews of Kindle devices, and plenty more.
Also, don't forget to check out the Blog for news and information about the Kindle and Kindle-related products.
Don't forget you need to Register if you want to become a member and leave comments.
Yes, KindleBoards is basically a forum site, but it is a popular one and continues to grow. A fiction writer interested in promoting his or her own work could do a lot worse than hanging out on these forums.
Let me add here that if you join the folks over at KindleBoards, please do not go in there all gangbusters and start promoting your e-books and other writings all over the place. That is considered spamming, and it is rude. If you look around the various forums, you will find a handful of posts where it is appropriate to market your works, but doing nothing but talking about your books is likely to bore and tick off others. Think about it: How often do you really like someone bombarding you with advertising? Most of us don't like it. Go ahead and promote in the places at KindleBoards where it is appropriate, but otherwise, take it easy. The best way to promote your work is to be yourself and become an active part of the KindleBoards community. Ask questions, provide answers, chat it up. Make some friends. If you are an accessible person to others, they will begin to notice. And when people begin to notice you, your e-book sales will improve.