"Particle Debris: * Twitter Personality Types" - http://ping.fm/qkh7f

Besides the ones described in the blog above;
How about the types described in the book, The Tipping Point:
Connectors are the people who “link us up with the world ... people with a special gift for bringing the world together.“
Mavens are “information specialists”, or “people we rely upon to connect us with new information.
Salesmen are “persuaders”, charismatic people with powerful negotiation skills.