Code2Flow - An easy solution to create product flows.
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.
CodeShare.io - Realtime code sharing for developers
Apache OpenOffice Draw - Makes drawing business processes and diagrams a snap!