Filta is a quick tool that let’s you search through the profiles of those people you follow. You simply use oAuth to allow Filta to access the list of those you follow and import them. If you follow over 200 people it will import the first batch and the rest happens later.
You then have a very simple UI where you search for keywords (even partials) on the upper left and it starts building a shorter list for you to browse.
Of course, this relies heavily on people using good keywords in the bios on Twitter. With it you could easily find an expert in a topic of someone with a common interest.
Searches can be saved so you can quickly revisit and use them again in the future. I tried some boolean searches which did not turn out well.
Otherwise a nifty little tool worth checking out as they possibly update it.