Clearbit - Clearbit provides Business Intelligence APIs
Product School - The global leader in product management training
ZoomInfo - ZoomInfo is a B2B database providing detailed business information on people and companies.
The Product Folks - A volunteer-led community of product managers and makers
DiscoverOrg - DiscoverOrg is an IT sales intelligence platform providing technology marketers access to data, IT org charts, and real time projects.
The Product Management guide - A book on how to create and ship products that people love