There are a wealth of changes which can be made to an Ubuntu system that sit in a category that is half way between the obscure and the genuinely useful. Ubuntu Tweak is utility that exposes these options with a handy GUI.
GIMP 2.7.3 has added one of the most requested features in the program’s history: a single window mode. Version 2.7 is part of the development branch, so unfortunately, the feature won't hit most distro repositories for a while.