It's only a piece of mdf (3 metres long by 1.5 metre high) which i painted blue with some blue matte paint that i found in our paint cupboard. It is suspended on a bench outside with someone holding it up from behind. I use it when it's cloudy, to get even lighting, and i place it exactly in line with the sun, so that no shadows are cast.
It's about as cheap as you can get!
I'll post some pictures when i get them.