I haven't yet finished up writing all the content I want to write about the process needed to get this working, but I do have a little teaser picture to share:
That is a Compaq LTE 5150 with a 100MHz Pentium CPU and 40 MB EDO RAM running Gentoo Linux! The kernel version is 4.2-rc1 (because I'm an incorrigible ricer), it was all built with GCC 4.9.3 and it is using the venerable musl C library instead of glibc. Boot up takes only about 15 seconds off the 5400 RPM laptop IDE disk, and once booted, the minimal kernel I have + bash use only about 3 MB of the 40 MB total.
It may not seem like a very useful thing to have done, but I had a lot of fun building it up, and I've ended up finding and closing various bugs in everything from procps to the kernel itself. So I feel that not only has this been a fun personal project across two weekends, but it has been productive for the entire community :)