TwitSeeker uses a custom built tag cloud (per the developer comments) that allows you to find Twitterers based on not their profile, but what they have recently tweeted about. The results are returned in a control panel format.
Now the good news, if you log into Twitter, you can then batch follow people, making this a following management tool also.
Before I published this I happened to catch a link out of the corner of my eye. While the front page is so simple and clean, they took the thought to add an Advanced Search link where you can specify all sorts of extras like:
- word inclusion and exclusion
- distance from a place (in miles or kilometers)
Limits are to be specially noted since you can go so far as to say only show me results for someone that has tweeted about this at least XX amount of times. This removes people that just pump links or never really talk about a topic. You can also specify the maximum number of pages of people to return and some other facets.