WP Optin Wheel - Gamified list-building for WordPress
draw.io - Online diagramming application
Insite - Dynamic content personalization WordPress plugin
Dia - Dia is a GTK+ based diagram creation program for GNU/Linux, MacOS X, Unix, and Windows, and is released under the GPL license.
SquareSpace - Squarespace is the easiest way for anyone to create an exceptional website. Pages, galleries, blogs, e-commerce, domains, hosting, analytics, 24/7 support - all included.
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.