For you Twitter users who are looking to further extend your network, take a look at
Twello.com. Here, you can select categories you're interested in, along with subcategories (Arts, Associations, Food, Small Business, Sports, Media) or you can search for people using your own criteria. What you get in return is a list of users, sorted by number of followers (or last activity), see where they are located and their URL.
At first glance, it looks like a pretty extensive list and not a bad way to add some followers. The service - a product of WebProNews - claims to currently index more than 382,000 people. And it doesn't look as crude as the image below.