Is there an alternative of wmctrl on OS X? It seems that wmctrl (installed from Homebrew) only works for X Applications on OS X.
You can do some of the things wmctrl can do on OS X via AppleScript. Here is an example.
Do some research into AppleScript. It can be very useful.
Also, there is an application called stay. Definitely doesn't have near as many options as wmctrl, but who knows, it might be all you need.
Per askers request, here is a free one! ShiftIt. I still recommend AppleScript, it is the hardest of the three to master, but it is also the most powerful.