I don't suppose there's a way to adjust window size by keyboard instead of by mouse? If there is, I'll write a macro for my programmable keyboard and just hit that key every time I open a window.
To change the size of the borders of the window without maximizing the window: Alt+Spacebar (to open the window menu), "S" (for Size), right arrow key several times, down arrow key several times, Enter key to confirm.
To maximize the window: Alt+Spacebar (to open the window menu), "X" (for maXimize).
Edit: And for situations where you're manipulating a child window (such as single document inside of a document editing program when there are several simultaneous documents open) it's the same thing except you use Alt+hyphen to open the window menu of the active child window, then the commands are the same.