In This Week in Google of a week or two ago, a tool was mentioned to find people on twitter that match your social graph. The tool is available at http://followfinder.googlelabs.com/ and simply asks you for a Twitter user name.
After entering your name, Follow Finder looks at your followers, and finds people that are similar to the people that you already follow, and people that have similar followers to you. The result page then shows you two columns:
So, if you’re looking for more people to follow on Twitter, try Follow Finder, and see if the people it suggests are what you’re looking for.