PreZentit - Prezentit is an online presentation solution based on JavaScript that comes with new online collaboration tools.
draw.io - Online diagramming application
authorSTREAM - authorSTREAM enables presenters to upload & share PowerPoint, Keynote & PDF presentations online; embed in blogs, convert to video and share on social networks.
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.
Zentation - Affordable webinar software. Create online presentations with synchronized video and PowerPoint.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.