YesInsights - Get Customer feedback with simple one-click or NPS surveys
Startup Growth Roadmap - Get from idea to product market fit
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.
OpinionX - Stack rank people's priorities in minutes with OpinionX's free ranking surveys.
TinyNPS - Simple NPS feedback
Product Fit - Measure product/market fit in app with your users.