From Twitterholic, here are some of the top-rated and most popular Twitterers. Some you may know and others have charm and appeal you'll have to discover on your own:

Industry folks

• Jason Calacanis, http://twitter.com/JasonCalacanis
• Steve Rubel, head of Edelman's digital practice (edges out Stephen Colbert in popularity and following), http://twitter.com/steverubel
• Robert Scoble, former Microsoft evangelist and author/journalist, prolific and committed poster about all things digital, http://twitter.com/Scobleizer
• Paul Walker, GCI's head of digital, http://twitter.com/paulwalker

Other popular personalities

• John Edwards, presidential candidate, http://twitter.com/johnedwards
• Barck Obama, presidential candidate, http://twitter.com/BarackObama
• Amber Macarthur, http://twitter.com/ambermacarthur
• iJustine, http://twitter.com/ijustine
• Stephen Colbert, http://twitter.com/StephenColbert "Viewers unite. You have nothing to lose but the facts…"

Twitter founders

• Evan Williams, http://twitter.com/ev
• Biz Stone, http://twitter.com/biz

I learned quickly from many of the sources referenced here. In fact, one of the most honest, open and public dialogues I've participated in lately was instigated between Steve Rubel, PC World and the rest of us. The post and commentary gives great perspective as well as some best practices to apply when you begin microblogging. Check out this open letter about a tiff that erupted from a Twitter post. It's good reading and also suggests some of the challenges of open blurting on both sides in the forever-archived world of blogs/twitters.
 
Here's a closing thought as you head out into the digital frontier. If Twitter were an acronym, I think T.W.I.T.T.E.R would stand for "The Way It Thinks, Travels, Evolves and Relates." Expect this smart, global phenomenon to expand its global scale while continually evolving based on who is connecting and using it.

We look forward to meeting you in the Twitterverse. Cheers!