Because of their small or non-existent footprint, micro-Linuxes are especially suited to run on laptops -- particularly if you use a company-provided laptop running Windows9x/NT. Or for installation purposes using another non Linux machine. There are several micro Linux distributions out there that boot from one or two floppies and run off a ramdisk.
Xdenu
http://xdenu.tcm.hut.fi/ , quotating Alan Cox: "Xdenu is a small distribution program that installs as a set of DOS zips onto a DOS partition and gives you a complete X11 client workstation."
SmallLinux by Steven Gibson
http://smalllinux.netpedia.net/ Three disk micro-distribution of Linux and utilities. Based on kernel 1.2.11. Root disk is ext2 format and has fdisk and mkfs.ext2 so that a harddisk install can be done. Useful to boot up on old machines with less than 4MB of RAM.
You may also consider some of the boot floppies provided by various distributions falling into this category, e.g. the boot/rescue floppy of Debian/GNU Linux.
If you like to build your own flavour of a boot floppy you may do so manually, as described in the BootDisk-HOWTO or using some helper tools, for instance mkrboot (provided at least as a Debian/GNU Linux package) or pcinitrd, which is part of the PCMCIA-CS package by David Hinds.
Also you might try to build your Linux system on a ZIP drive. This is described in the ZIP-Install-mini-HOWTO.