Twitter: You can follow me on Twitter here. Be warned: I occasionally tweet about things other than books (food, technology, etc.).
Facebook: My Facebook author page is here. I probably don't spend as much time there as I should, but it is dedicated to things related to writing and the book industry.
Other: I also have a personal site and blog here. I sometimes write about, well, writing - but a most of it is more like "random thoughts I had and I want to share."