An approach to pack arbitrary sized textures in one big texture. This is useful for example when saving lightmaps as they will be small and in a large quantity so you don’t want to resize them all to power of twos’ and save them separetly.

 An image of the result of a packing of a big amount of lightmaps, the padding in white is just for making the different maps more visible.

Link to the source:
http://www.blackpawn.com/texts/lightmaps/default.html