I've upgraded Boulder Twits so that everyone listed has their own personal map, in addition to the graphs showing the whole community. They show who you talk to most on Twitter, organized into groups based on who they talk to. As an example, here's my personal graph. There's some clusters that represent different networks I'm in contact with:
The Boulder folks are mostly in a small, tightly-connected pack on one side. It's almost a mini-version of the full community.
Only a few of my Apple colleagues are on Twitter, but they're all pretty interconnected too.
Walter Olson is the founder of the Overlawyered legal blog, and as you can see both me and Jeff Nolan are big fans.
Stay tuned, I'll be using this data to answer some questions like "Who are my friends talking to that I should be following?".