StrikeIron Reverse Phone Lookup API

From their site: The StrikeIron 24-hour Accurate Reverse Phone Lookup Web Service provides a programmatic interface to name and address data associated to any telephone number, including residential, business, and government numbers in the U.S. and Puerto Rico. This data is updated nightly making them the most accurate and up to date resource of their kind. Accurate directory listings are a fundamental need of every business and government agency. Each year, up to 60% of directory listings change, causing records to quickly become obsolete. Businesses have had to rely on labor-intensive and inaccurate sources in an attempt to keep records up-to-date, using processes that are both costly and ineffective.
Read More