Incoming Feedback by Hotjar - Instant visual feedback for your website or app!
draw.io - Online diagramming application
Customer Feedback Portal - Ask customers what you should build next
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.
Feedback Fish - Collect feedback & make your customers happy.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.