draw.io - Online diagramming application
Delighted - The fastest and easiest way to gather actionable feedback from your customers
LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
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!
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
Wootric - Wootric is software that allows apps and websites to take customer satisfaction surveys so that you can properly gauge the popularity and success of your app through the eyes of the people using it. Read more about Wootric.