Jeremy Tanner passed along a couple of great automatic lists of top Boulder twitterers. Twitterholic uses raw follower numbers to rank its list of over 400 locals, and Twitter Grader (by one of my favorite bloggers, Dharmesh Shah) has a more nuanced list sorted by influence. When I was building my first draft, I also used Twitter's own advanced search to look at all the updates within 15 miles of Boulder, which helped me discover some interesting people.
I've been digging through all these looking for accounts run by individuals rather than groups, and for people that have a technology connection. Together with some of the Imulus folks, BoulderTwits is up to 50 people, and I'll add more over the next few days.