I finally found a site that lists all of the hashtags being used on twitter.  Hashtags are tags added within a tweet followed by pound sign (ex. #hashtag).  According to the site...

"Hashtags was designed to accommodate the real-time news community. We provide analytic reports and indexing features to allow users to track what's happening now."

Hashtags are listed alphabetically, by popularity, and by the number of times they have been tweeted.  I'm still looking into the people search. This site is exactly what I asked for a while ago. I cannot even remember how I found it.