I find IPE to be a life-savior when it comes to generating physics illustrations which come with their share of math toppings. The editor has nice utilities for latching on to the boundaries, intersection, center etc of geometric figures. The spline tool is the best I have seen anywhere. Layers are handled with grace. LaTeX is rendered instantly. It is very easy to produce a multipage document. What more can one possibly want?
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Kissflow - Kissflow is a workflow tool & business process workflow management software to automate your workflow process. Rated #1 cloud workflow software in Google Apps Marketplace.
LaTeXDraw - LaTeXDraw is a graphical drawing editor for LaTeX.
ProntoForms - ProntoForms is a mobile business solutions application, converting paper forms onto any tablet or mobile device.
draw.io - Online diagramming application
Nintex - Cloud-based digital workflow management automation platform