[Note: Some of these links and sites mentioned are no longer active.]
I don't maintain a web page myself, but fans and friends have been kind enough to put up some for me.
There's a lot of bibliograpic and biographic info at the SFWA website at: http://www.georgerrmartin.com/
And there's a list of some of my out of print books for sale at: http://www.horrornet.com/georgerr.htm
A number of Seven Kingdoms websites (more every day, it seems) have been established to discuss A SONG OF ICE AND FIRE and "The Hedge Knight." The oldest of them is Dragonstone, which can be found at: [url=http://www.users.bigpond.com/dragonstone/]http://www.users.bigpond.com/dragonstone/[/url]
If you follow the links from Dragonstone, they will take you to the rest of the sites.
All that being said, I'm afraid I don't answer questions on most of these sites. Some of them can get very busy, and I'd rather spend my time =writing= the books instead of answering questions about them. Also, I prefer to let my readers kick around their own theories and viewpoints about the books, and the author's presence would inevitably inhibit such free-wheeling discussion.