Inkscape, when I want them to look really nice and am willing to put some time in to making them look the way I want. I've also used kivio on occasion, and gra

Inkscape, when I want them to look really nice and am willing to put some time in to making them look the way I want. I've also used kivio on occasion, and graphviz, and ploticus. Again, all depending on what I'm after.