Peter,
The answer depends on how tightly you specify the question. If you are talking
about in situ fabricated structures, probably the Swedish group with the boron
deposited spirals and spikes (Westberg, et al.) wins. If you allow for "some
assembly required" (a la Pister hinges), we have done things several
millimieters tall. Who knows. I think the fold up stuff (even though we do it)
is not comparable to the "truly 3D" stuff. It's like comparing origami folding
to casting.

Best Regards,
Greg

P.S. This sounds like a contradiction in terms... if it gets so tall, is it
still MEMS (i.e. "micro")?