AbTest.io - A free url shortener with A/B testing features
UserTesting.com - Usability testing has never been easier. Get videos of real people speaking their thoughts as they use websites, mobile apps, prototypes and more!
GoodUI Evidence - People's A/B test results that show which UI ideas work best
Instabug - The top apps in the world rely on Instabug for beta testing, user engagement and crash reporting.
PreFlight - Preflight is an Automated Web Testing tool. Allows everyone to automate Web UI tests.
Userbrain - Easy, fast, and affordable user testing for websites and prototypes.