US Data Corporation - From their site: "The highly experienced list consultants at US Data Corporation can take the pain and difficulty out of the list selection process. The chances are very good that we have succesfully sourced a list for an offer just like yours many times in the past and already know what will work and what won't. The three principal categories of marketing list are: Compiled Data - This is regularly updated data pulled from public records such as postal records, county recorder offices, government records, telephone directories, and credit bureaus. This type of data is best used when demogrpahic criteria is the best method of targetting your most likely prospect. Response Data - These are privately owned files that are collections of people who have had to take a specific action to get on the list. Subscribing to a magazine, purchasing a product, filling out a warranty card, entering a sweepstakes, and joining a club are all examples of the kind of actions taken that qualify someone to become part of a response list. Sales Leads - These are proactive requests from a prospect indicating an active interest in purchasing a specific product or service."