What are some alternatives?
When comparing Gilbert Data Base and Lead411, you can also consider the following products
TelephoneLists.Biz - Telephonelists.biz is the source for phone leads for sale, provides the agents with a wide audience full of leads ready to become the next customers.
ZoomInfo - ZoomInfo is a B2B database providing detailed business information on people and companies.
Salestools - Monitor your Linkedin newsfeed for keywords to obtain leads.
InsideView - InsideView aggregates and curates all the company and contact data, news and social insights, and professional connections you need to do business better.
Statlistics - Statlistics is a list management and brokerage firm specializing in business and consumer list solutions.
Clearbit - Clearbit provides Business Intelligence APIs