The FastDoom port slims down some floor textures and such and makes Doom playable (and not stamp sized) on a 386.
About the 386, you could run SICP as a GNU Info file blazingly fast and a Scheme compiler on another TTY, or under GNU Screen.
You could typeset with Groff and Mom, too.
Now try running LaTeX on that. Yes, Donald Knuth is the Ur-creator on CS and typesetting, but hey, sometimes you don't need a full 3GB Texlive suite to typeset some book or math equation notebook.