Windownaut is a lightweight and robust window resizer, mover, and more, that aims to have a very small footprint. It allows you to easily resize, move, and add a variety of new control options to almost all app windows. Does not use any system hacks or tricks: it works using standard magical Apple APIs.
Fully functional 14-day trial with a reminder for every 10 operations performed.
Updated on Sep 11 2016
Note: Now requires OS X 10.10 or later running on a 64-bit Intel processor