The shortest, most elegant one I know of doesn't even
require a
compile:
Just type in :(){ :|:&};: at the bash prompt and hit return.
By the way, the fork bomb has lost its bite on modern hardware (under i386 running Linux, at least) because it will die out when the upper limit of processes is reached, and pretty much any processor above Pentium level won't be overworked in getting there.