Hunter - Find all the email addresses related to a domain
draw.io - Online diagramming application
AnyMailFinder.com - Find anyone's email address
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.
EmailMatcher - Find anyone's email address in a matter of seconds, for free
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.