It used to be, in the good ol' days, "about 4 floppies of kernel and drivers", and "12 floppies of baseutils" with your added "5 floppies for emacs" and "1 floppy for vim" .. but those days are long over.
Nowadays, the most useful 'self-building' OS/bin stack is debian with build-essentials.
Better pointers: http://landley.net/aboriginal/about.html via more googling: https://encrypted.google.com/search?hl=en&q=minimal%20self%2...