Libre office draw is wonderful, it can edit pdf docs at ease. It’s crazly powerful compared to paint 3d
draw.io - Online diagramming application
Cardhop - The Mac contacts app you'll want to use.
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.
Webby - Webby allows to use Facebook, Youtube or any web app as a regular desktop apps, integrated with the...
Dia - Dia is a GTK+ based diagram creation program for GNU/Linux, MacOS X, Unix, and Windows, and is released under the GPL license.
NetHunt CRM - Turn Gmail into a smart CRM