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!

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

Validately - Validately is a user feedback platform to test demand and usability on a clickable prototype or live feature.

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

UserZoom - Test, measure, and monitor UX with our cost-effective all-in-one platform. UserZoom is a cloud-based solution for online usability testing.

Marvel - Turn sketches, mockups and designs into web, iPhone, iOS, Android and Apple Watch app prototypes.