[Henry] Hook has come to be known as the Marquis de Sade of the puzzle world: a brilliant and oddly beloved misanthrope, administering exquisite torture through dozens of puzzle books and syndicated crosswords.
A functional self-replicator has been designed for Conway's game of life. The deceptively simple automata 'Conway's game of life' is a model system that illustrates how simple 'physics' can give rise to incredibly complex phenomena. Although a menagerie of existing patterns have been discovered/engineered that display a variety of interesting behavior (eg here), there are also many unanswered questions about what is possible within the simulation. Recently, life-enthusiast mscibing succeeded in designing a universal constructor pattern that is capable of building a functional copy of itself. Its execution can be viewed directly (though it takes a while!) using Golly, a sweet, open-source app for viewing life simulations, as well as other cellular automata.
Want it? Make it! 3D printers aren't that new -- already there are robots that print houses, inkjet printers that print human tissue, and for you CSI fans, machines that can reconstruct bullets, among other things. What's new, you ask? Machines that can produce anything and self-replicate, too. All under a GNU General Public License.
Bored? Maybe this little doo-hickey will entertain you for some time. It sure did for me.
The most fun I've had with an applet, ever. [From Eatonweb.] This just isn't getting linked to enough, so I had to post it somewhere else. Make sure you read the bit in the instructions about muscles, otherwise you won't get very far. If only there was a way to save configurations . . .