Softlanding Linux System (SLS) was an early Linux distribution, founded by Peter MacDonald in mid-1992. It was the first to offer a bootstrap install disk from floppy, cdrom, network, etc. It was also the first comprehensive Linux distribution, containing more than the Linux Kernel and basic utilities, plus early GNU/Linux features such as the X Window System and TCP/IP.
SLS was probably the most popular Linux distribution at the time. It came in a handful of files that you would unzip and copy to floppy disks. This was Linux's first big breakthrough. SLS dominated the market until the developers made a decision to change the executable format (if you remember the a.out to ELF conversion you'll remember this). This was not well received by the user base. Just around the time this happened Patrick Volkerding had taken SLS and adapted, modified, tweaked and cleaned it up making it a different thing all together. He called it Slackware. With the unpopular direction SLS had taken, Slackware quickly replaced it and became the dominant distribution used by nearly everyone. In fact it's still in use today.
Similarly Ian Murdock frustration with SLS lead him to create the Debian project.