PGF and TikZ - PGF/TikZ is a tandem of languages for producing vector graphics from a geometric/algebraic...
LaTeXDraw - LaTeXDraw is a graphical drawing editor for LaTeX.
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Diagrams Haskell package - Diagrams is a powerful, flexible, declarative domain-specific language for creating vector...
Graphviz - Graphviz is open source graph visualization software. It has several main graph layout programs.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.