Web presence. I had heard that I needed one. But as to why and how, I didn't, still don't, have clear ideas. Creating a website involves either a steep price or a steep learning curve. I checked out MySpace and found it too vast and overwhelming. My targeted readers at this point are middle-graders, who may not be as active on such sites as the target audience of YA books.
A blog then. It's easy enough to set up. I was uncomfortable when I started it. Still is, a little bit. Face it, the world needes another blog like we need an extra 6-inches of fat around our waists. But I thought I'd just give it a try. I do like reading some blogs so mine could potentially be not a complete waste of time. Besides, as someone who has a problem with finishing a project (preferring instead to tweak and worry it to death), a blog forces me to produce a finished product every few days.
Janet Friedman's May 22 post on http://blog.writersdigest.com/norules/ covers the topic very well. She touches on the different ways to have a web presence: websites, blogs, social sites, etc. She has specific advice for writers who haven't yet published a book and those who are published.