The tiny Linux category is filled with excellent, stripped-down specialized Linuxes for all occasions, from desktops to servers to routers to Internet kiosks, and everything else you can think of. They run on embedded devices, router boards, commercial wireless routers (like the Linksys WRT54G series), PCs, blades, USB sticks, CDs and the sleek new IDE flash solid-state drives.
A common difficulty with these tiny Linuxes is adding or removing software and upgrading because package managers are usually jettisoned to save space. So you have to copy binaries and libraries to add new applications, and upgrading often means re-installing the root filesystem.
But somehow the Voyage Linux developers figured out how to shrink Debian Sarge to less than 64 megabytes while retaining the apt-get package manager.
Voyage Linux is pretty amazing. The stock image can be run from a bootable live CD or installed into any storage medium you want. It supports all bootable media, including PXE network boot. It's designed for wireless routers, but because it includes apt-get it is easily and highly customizable. If you've been wishing for a tiny Linux you can easily tweak to meet your needs, starting from the smallest possible image and adding what you want, this just might be it.
The LiveCD is a mere 31-megabyte .ISO. It requires a minimum of 64 megabytes to install on any other medium, which of course these days is not a problem. In fact, it's getting hard to find any kind of bootable storage media that small. Many older router boards have permanent, non-upgradeable 64-megabyte Flash storage, however, so targeting this small size is a good thing.
The stock Voyage Linux comes with a 2.6 kernel and support for a number of wireless interfaces, include Prism54, Atheros, Intel and Ralink. It has all the pieces needed to build a good wireless access point with strong WPA/WPA2 encryption: HostAP, wpa_supplicant and captive portals. It supports PC Engines WRAP boards, including hardware watchdog and a temperature monitor.
Visit the Voyage Linux Wiki for downloads and documentation. You may also find it bundled with wireless routers at various vendors.