AbTest.io - A free url shortener with A/B testing features
Usersnap - Visual Feedback - Usersnap helps your business with its versatile feedback platform to build better, more successful products and services with the help of user feedback. Collect feedback along your product development lifecycle. Try it for free.
GoodUI Evidence - People's A/B test results that show which UI ideas work best
Feedback by Pixelic - Painless design feedback and version control.
PreFlight - Preflight is an Automated Web Testing tool. Allows everyone to automate Web UI tests.
Sesov - A community for anonymous design feedback