BasicLinux
BasicLinux is a mini Linux distribution optimized for old (386 - 486) PCs.
It's based on Slackware, using a small kernel (2.2.26) and busybox to provide a low-RAM Linux, capable of browsing the web, doing email, and functioning as an X terminal.
It's offered in 2 versions. A Hard Drive one that boots from DOS, and a floppy drive one, that uses 2 disks.
Both versions can be used with a 386 CPU. The Hard Drive installable version requires 3 MiB of RAM and 20 MiB of space in the Hard Drive, plus a bootable DOS. The floppy version needs 12 MiB of RAM.