Advanced flowchart techniques

BoUML-it is free!

I have used this open source tool for the last 6 months at work to create UML diagrams: bouml.free.fr/

I have used it on both a Macbook running OS X and Ubuntu Linux on the desktop and with success. It does codegen too (although I haven't used this feature myself). If you are creating a diagram from BoUML you can right click -> Tools-> HTML etc. Etc., and also create and actually create a diagram - this will create a whole tree of html, css, etc. And will include .png, which you can later import into a Word-like document.

If you are new to UML and want to learn this route, I suggest UML Distilled by Martin Fowler as a quick build-up. I still use this as a reference when I collect diagrams and I forget some of the syntactic details;) The best part about UML is that most programmers will understand it. If you don't feel like buying the book, you can of course Google UML Tutorial and get a lot of free information.

Non-UML:

You can also use an open office drawing app to do some simple flowcharts. It has some good non-uml forms, so if you're not trying to be "strict" in the UML conformance sense and just want a simple flowchart this might be a good choice.