Eric Gunnerson points to a post by Jeremy Rule about how he flash-cooked a hamburger using a giant Fresnel lens.  Pretty groovy stuff, although Jeremy says the burger wasn't very tasty.  It got me thinking, though, that a really fun project would be to take one of those giant Fresnel lenses and see if one could build a miniature solar-thermal generator, like these.  A nice big cast-iron pot with a lid, a few holes drilled, very small steam turbine...  See where this is going?  Unfortunately I'm way to lazy to actually try it myself.  I haven't even gotten around to trying out the DIY solar pizza oven.  :-(