Wikipedia
Nanolinux
NanoLinux is an open source, free and very lightweight Linux distribution that requires only 14 MB of disk space including tiny versions of the most common desktop applications and several games. It is based on the Core version of the Tiny Core Linux distribution and uses Busybox, Nano-X instead of X.Org, FLTK 1.3.x as the default GUI toolkit, and SLWM (super-lightweight window manager). The included applications are mainly based on FLTK.