As someone who made his kid's own sleeping situation, I will remind everyone that the first, middle, and last step of any crib hacking project is studying the CPSC's safety and testing requirements, and then assuring that your design meets them.
And with that out of the way, let me also say that I'm pretty damn impressed with the inventiveness and the build quality of the low-slung co-sleeper Pregonaut made from an Ikea Sniglar changing table.
Those Sniglars have always been a mystery to me, almost as much as the idea of loading one's bed up with cats and babies.
I'm such a hack [pregonaut via ikea hacker]
Sniglar Co-sleeper hack photoset [flickr]
Sniglar changing table, $39.99 [ikea]