General A* Pathing tutorials

Hey guys. I'm working on a very simple battle chess style game. The units themselves are free to move about based on their properites (speed, range, etc.). I need to learn how to teach my 'bots' how to find their way from say grid square 0,0 to 5,3 and re-adjust on the way if some other 'bot' moves to a square involved in the path.

Does anyone know of some good resources, demos, etc. where I can learn the basic approach?

Thanks ahead of time! :)