Cute... It reminds me of proofs my father designed into a barn he built years ago.<p><a href="http://waiveris.com/project/fractals/barnwindows/" rel="nofollow">http://waiveris.com/project/fractals/barnwindows/</a>
I like that it's animated; nearly every static "visual proof" of the Pythagorean theorem is nearly incomprehensible to me without a lot of explanation---I'm a <i>huge</i> fan of visual proofs but for most of them you really need a time dimension to make sense of them.
Another cute way that's more obviously correct without translations is to consider a square with sides of length a+b. You get an interior square of area c^2 and 4 right triangles with legs of size a and b.
Nice animation, but I think in the last step when c² is mentioned (after "a² + b²"), the c-square should be restored such that it is again visible as square.
If you like this sort of thing, definitely check out this book: <a href="http://www.amazon.com/Proofs-without-Words-Exercises-Classroom/dp/0883857006/" rel="nofollow">http://www.amazon.com/Proofs-without-Words-Exercises-Classro...</a>