This is my self-made, extreme macro set-up. I have reverse mounted an old 23mm Sigma lens onto some extension tubes. It sits together with my Canon 600D on an improvised mount and sample holder which is made from Meccano, some aluminium sheeting and old microscope parts.
Together with a ring flash it works well. I can get objects which are 5mm wide to fill the whole chip, giving me images of about 4.5 times life size. I played around with some other set-ups: stacking the reverse mounted 22mm Sigma lens on top of my 250mm zoom, on top of the extension tubes. This gave me 12 times life size, but it was unwieldy and there was quite some distortion.
I tested it on a feather and you can see crystal like spots of light which are the barbules. A friend of mine first showed me this kind of set-up being used to photograph snowflakes. It's taken me more than half a year to build this but now it's finished all I have to do is wait for the snow.