LEGO is a brilliant medium. Love these, and so many of the plethora of "MOC"s out there.
That RA300 is glorious, reminds me of the Lotus 43 someone else made a while back.
I've had a bit of fun with the virtual building space provided by LEGO's Digital Designer as well. http://ldd.lego.com/
I most recently used LEGO (technics) for engine configuration testing. By hooking weights up to the pistons, and modifying "crank" parts to phase them correctly, you can test balance and smoothness to verify theory.