http://youtu.be/QxenERXuoQU
Alrighty, this question comes up a LOT, so anyway, decided to make a new video on it, that is a bit more polished than my previous one. This does not count as the tutorial for the week.
Using this you can install:
Patterns in Gimp
Brushes in Gimp
Scripts / Script-FU in GImp
Plugins in Gimp
Gradients in Gimp
Themes in Gimp
and More