Twitterholic added a couple of neat features.
First, they now sort Twitter users by when they joined.
They also now sort Twitter users by location. So, for example, you can now see who has the most followers among San Franciscans or New Yorkers.
In addition, you can also sort Twitter users by the number of updates or by how many they follow.
Finally, you can combine these. So now it's easy to find out who in New York has been on Twitter the longest. In addition, you can also now track the overall top 100 list via RSS. Here's the feed.
