Fuzzy/distorted glow/blur effect via shaders?

Hey everyone. I've been playing around with shaders just for fun but I've run into a few things that I've got no idea where to start with.

This is the sort of thing that I am going after - with the blurred colours on the cube(the fact that the insides aren't blurred on the picture is just me drawing it wrong though). Where would I start to write an image shader that does something like this? I just have no idea how to distort the image.

Thanks in advance.