Easy User Test - Easy User Test is a user testing tool that offers the easiest way to test your text and design.
Useberry - User testing feedback and rich analytics in minutes
Preely - Remote user testing and rapid prototyping
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!
Marvel User Testing - Record what users do with your designs and sketches. Free!
Maze - Beautiful & actionable analytics for InVision prototypes