draw.io - Online diagramming application
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
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.
Splash - Anyone can create a Splash event, whether you're a company hosting a single event or an individual hosting a personal event like a birthday or wedding. Get Started for Free. Text goes here. X. Full Event Program.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
Eventzilla - Eventzilla lets you sell tickets online and manage attendees from one integrated application.