A lot of ambigrams can be found here:
replies(1):
"The Ambigram deck itself seems impossible at first, and in fact, it would have been impossible just a few years ago. No human being could have designed it alone, even if they possessed several lifetimes to work on the problem."
which is exactly what Cerulean's page refutes - it's a hand-designed 7x7 grid where each word transforms into each of the other words.