amCharts - Advanced javascript charting library that will suit any data visualization need
Dia - Dia is a GTK+ based diagram creation program for GNU/Linux, MacOS X, Unix, and Windows, and is released under the GPL license.
Active Artist - Cross Platform, Geolocated Analytics for Booking Agents
draw.io - Online diagramming application
Quickmetrics - Here you'll find some handy helpers to send events to Quickmetrics. - Quickmetrics
yEd - yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.