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

Appcues for Product Adoption - Make your product easier to use. Code-free.

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

Usetiful - Fight user churn with great user onboarding. Interactive product tours and smart tips significantly improve your user retention.

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

UserGuiding - User onboarding made easy, for less. Create product walkthroughs in a couple of clicks, without breaking the bank.