Floor van Lamoen, mentioned this on the Geometry Puzzles newsgroup
I think it's fascinating. The grid shows a red 8x3 triangle a smaller green one and two purple and yellow shapes of area 8 and 7. Rearranging the pattern seeems to leave one square missing. I wonder why...? Clever, innit.. The same trick can be applied with other Fibonacci configurations sometimes with one square too many, at other times one square too few.