Twellow

Twellow, at http://www.twellow.com is another great way of finding people to interact with. People here are categorized into all different areas and you can search for those with similar interests to your own.
The main page shows you all the categories, which then have sub categories as well. You just click on a category and the list of people in that area are displayed.You don't have to be registered with Twellow to be displayed, but at the time of writing there were nearly two million people showing on the site, so you will have plenty to choose from. By all means though, register yourself and set up a profile so others can find you.
When you click on a category, Twellow displays a list of people in that category and they are ordered by the number of followers they have. If you are already logged into Twitter via the web, (not Tweetdeck), you will be able to follow people directly from the screens where the profiles are displayed.