Ok, so the power-of-two rule hasnt annoyed me so much, because I can just rescale it in OpenGL to make it non-power-of-two etc etc, but one thing that's boggled my mind, is how to use textures that arent squares...
So far I can use squares, that's all well and good, but supposing I want to use a 640x480 bitmap as a texture, how would I go about it?