If you're looking for a business connection across social networks, Google is a great tool. I often do a search of Twitter + name, or LinkedIn + name to find a profile. LinkedIn, of course, has a great internal search engine (especially the paid version) and there are also sites like Data.com to find connections. More often than not, I utilize Google though. It's free and it's accurate!
RecruitEm was especially built for recruiters to easily find candidates for employment opportunities online. It's basically built to automatically construct complex boolean search queries to better search Google for the information you need. It's also a great tool for sales professionals who are trying to find leads via social media sites LinkedIn, Google+, GitHub, Xing, Stackoverflow and Twitter.
Once you've entered all of your information, the search query is constructed: