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.
Mastercam - Mastercam's Dynamic Milling is a game changer for us.
LaTeXDraw - LaTeXDraw is a graphical drawing editor for LaTeX.
CamBam - CamBam CNC software, best value for money, feature rich, CNC Software for G-Code generation on CNC Routers, CNC Mills, Homemade CNC machines, for 2D pocketing, 2D profiling, Text Engraving, Photo Engraving and 3D carving.
draw.io - Online diagramming application
Carveco - Carveco™ software is the trusted CAD modelling and CNC machining solution to a wide vatiety of industries worldwide.