I've had a few people ask me about how to track runners during the marathon. There are a couple of ways to do it - one is through the AT&T athlete alert program. You can have them send you text messages and/or e-mail updates. It's probably best to sign up for this as soon as you can - I think the cutoff is 6am on race day. You should received messages when the runner you are tracking crosses the 10k, half marathon, 30k and finish. Although I think there is some delay - so, don't expect to get the messages in real time.
The other way is through the Hewlett-Packard Athlete Search. You can see every 5k split - and from my experience this set-up is not as delayed as the text messages/e-mails. I think you can just search by name for both of these services - but, it's always helpful to have the race number as well (mine is 1143). There isn't any sign-up need for the HP search - it should be displayed on the Boston marathon homepage on Monday.