simple solution to this is to put whatever window to whatever program on the monitor you want to the extent of:
if you want on the left monitor, you need to dock it to the far left half of the screen using the "snap left", then close the window, next time it will open in that same location.
if you want a certain window open on the right, then set it to the right monitor, and close it, then next time it will open on the right.
you can even do this specific with thing like certain people you talk to through xfire, specific to whoever you set on one monitor or the other, will always open in that last saved position.