I was looking for a free flowcharting solution to help plan programming and game play. I am testing this first one right now and it seems cool, There is a free version and a $20 per year richer one. You create flowcharts in your browser and can store, share and collaberate.

http://www.gliffy.com/index.shtml

There is also Freemind which I've used on and off for several years. It is mind mapping software and also useful for certain types of planning.

http://freemind.sourceforge.net/wiki/index.php/Main_Page