Product Resources List - The biggest list of free product management resources

Zendesk - Zendesk is a beautiful, lightweight help-desk solution.

Product Wednesday - Every Wednesday, receive a handpicked selection of tools made for Product Managers, Product Designers, UX Researchers and every member of the Product team.

Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community

Intercom on Product Management - The ultimate resource for aspiring product managers

HelpScout - Help Scout is a simple, straightforward way to provide excellent support