Tweepz is probably the best Twitter search service for finding people based on keywords or names.
If you’ve ever wanted to find people on the fly, Tweepz would be your best bet. You can refine search results to only include users with a specified amount of followers, that twitter using a specific language, and more. It also offers search filters unlike TweepSearch. However, TweepSearch allows you to search within your followers, which Tweepz doesn’t offer.
When new topics of interest arise, head over to Tweepz and do a search for users that are listing those topics in their profile. Go ahead and give it a try!