Tool for drawing automata and syntax trees

Question

I am looking for a free tool to create visually appealing state machine diagrams and syntax trees.
Note. I just want to draw diagrams. I do not need to create a model or do something with it.

Thank you for your time.

EDIT :
I can add that I am creating documentation in Latex, and therefore I am also open to tex based diagram solutions.

Answer 1

Does Graphviz fit your needs: creates diagrams from text example: http://www.graphviz.org/Gallery/directed/fsm.html