For those of you who don't like diagramming and have lot's of original designs, than hopefully this will motivate you.
I have put together a small thing on Inkscape which will start you off in your diagrams. It has all of the arrows and has the first square drawn and some small tutorials on how to do the basics in diagrams.
You can download it here:
http://uploading.com/files/ee2a53ab/starter.svg/
I will update it every now and then, and if there's anything you feel i should add, then please don't hesitate to ask.
And before downloading the file above, make sure you have http://inkscape.org/ (inkscape) installed on your computer.
Hope this help a little with your diagrams!

Josh