Not only does Whitepages.com have a powerful search feature for finding individuals, but I find its most valuable aspect is its Reverse Lookup feature. If you are interested in finding out someone's information based on a phone number, this is a great tool. What makes this particularly valuable is the feature that will tell you if the number you have entered is unlisted, or a cell phone.
While Whitepages.com is great for finding residential information, MPL subscribes to a great database for looking up preliminary business information.
ReferenceUSA is a database that allows you to look up both residential and business information. It is especially helpful for business information. You can sign on to it from MPL's website under Research Resources, and then by clincking on Featured Databases. You do need to have a current library card to access ReferenceUSA remotely, and it's also available within all City of Milwaukee libraries.