Trackingplan - Ensure the quality of your digital analytics.
Dia - Dia is a GTK+ based diagram creation program for GNU/Linux, MacOS X, Unix, and Windows, and is released under the GPL license.
Talkwalker - Talkwalker Consumer Intelligence Platform: built for speed of insight, ease of use, and data democratization
draw.io - Online diagramming application
Treblle - Mission Control For Your APIs
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.