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.
LibreOffice - Math - Math, LibreOffice, math editor, ODF, OpenFormula, open standards
LaTeXDraw - LaTeXDraw is a graphical drawing editor for LaTeX.
Math Magic - MathMagic Equation Editor for Desktop Publishing software & Word Processors, Adobe InDesign, QuarkXPress, MS Word, iWork, for Technical writing with very easy interface and fast input.
draw.io - Online diagramming application
KLatexFormula - KLatexFormula is an easy-to-use graphical application for generating images (that you can drag and...