Selenium - Selenium automates browsers. That's it! What you do with that power is entirely up to you. Primarily, it is for automating web applications for testing purposes, but is certainly not limited to just that.

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!

Watir - Watir stands for Web Application Testing In Ruby. It facilitates the writing of automated tests by mimicking the behavior of a user interacting with a website. CommunityWatir stands for Web Application Testing In Ruby.

Userbrain - Easy, fast, and affordable user testing for websites and prototypes.

Retest - Retest allows you to check your web apps user experience and deliver absolute masterpieces on multiple devices so that every time your customer visits your webpage, they feel what you want them to feel with your design irrespective of their device

userinput.io - Get on-demand feedback for your app, website or idea. Learn how to improve by hearing real opinions.