I've made this program and posted it on most of the forums I go on all the time but remembered most everyone here races so I though it would be great for you all.
It basically does math for you to find ratios, rollout, est top speed. Then it has some features for brushless and li-po batteries.
You can download it here. http://sourceforge.net/projects/rc-gear
Tell me what you think. Also I'm guess most of you have ideas for stuff to be added/changed. All help is greatly appreciated.