Wootric - Wootric is software that allows apps and websites to take customer satisfaction surveys so that you can properly gauge the popularity and success of your app through the eyes of the people using it. Read more about Wootric.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
Growth Score - 40+ companies share their Net Promoter Score secrets!
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
Customerville - Net Promoter Scores on steriods
HelpScout - Help Scout is a simple, straightforward way to provide excellent support