DrawPortal - DrawPortal is a drawing app that enables users to create beautiful drawings.

malmal - Draw together on a nearly infinite canvas with your friends or with strangers.

UMLGraph - UMLGraph is a professional automated drawing tool that allows the designers the declarative specification and drawing of UML class and sequence diagram.

Anondraw - Draw and paint live with friends or strangers on a big canvas. There is also a gamemode and gallery.

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.

Dia - Dia is a GTK+ based diagram creation program for GNU/Linux, MacOS X, Unix, and Windows, and is released under the GPL license.