I've run across some writers that don't know what Twitter is, or look down on it as a crazy time-wasting energy-suck. And surely it can be... you can even track how many hours you've spent on Twitter with Tweetwasters.
But for writers looking for sources, subjects or media/PR, there are very few other sites out there that can beat the instantaneous nature of Twitter.
Here are some Twitter people, aka Tweeps to follow, other than ME of course:
I use an application called Twhirl that pops up the “tweets” every few seconds. Because I follow a lot of other writers and media types I tend to know where the great blog posts are and if something is relevant to my current writing, I can include it… plus I try to never forget to tweet my own blog posts and I get more comments and my site hits go up. I’ve noticed my ad revenue go up as well.
There are some netiquette rules to follow of course, just like any other online tool. You don't want to break them, but it's ok if you make a few mistakes... just get out there and try it!