[unfasten]

>...either: A. Drag it to where you want it, and then fiddle around resizing it so that it's big enough and doesn't overlap anything else important...

Try out Winsplit Revolution. The help page gives a nice overview of the functionality: http://www.winsplit-revolution.com/help

It's free and works great for positioning windows. You can position windows using hotkeys and create custom positions/window sizes. WIN+ALT+Numpad 7 will place and resize a window in the top left of the screen, WIN+ALT+Numpad 6 will place a window on the right side of the screen and take exactly half the width, etc. It's become second nature to me and I rarely have to worry about manually placing a window.

[ashleyw]

Also Divvy for OS X which does the same kind of thing.