This started out as a gist that Jamie and I forked back and forth adding more and more implementations of factorial.
You can see the original gist at gist.github.com/309771.
As it became bigger it became impossible to store as a gist and would either have to have become one big gist or an individual repo and for the sake of syntax highlighting and this funky README the choice seemed obvious.
All the snippets start with an author's name in a language specific comment.
Feel free to fork the repo and add your contribution by creating a new snippet or just by optimising an existing one.