Follow @user's followers
The simplest way to find and add people with the same interests as you on Twitter is to find a popular tweep under your topic, say 'phpc' or 'techcrunch' for the geeky people like myself, and add people that follow these known users or communities. (@user's friends instead?)
About this tool
The most common way to find and add people with the same interests as you, is to find a popular tweep within your area of interest, say "mashable" or "techcrunch" for technology news, and add people who follow these known users.
Tweepi helps you analyze and filter tweeps out - the geeky way, with numbers in a table - based on their activity and sociability. We spent so much time perfecting Tweepi that now you can also sort and search (filter) the results anyway you like on per page basis.
Premium Tweepi users can do that for all users they follow or following them, not just for the current page, along with loads of other time saving features.