A tiny and surprisingly featureful webserver.
The full version, containing some documentation and configuration instructions. Builds as a single file with gcc or any other C compiler.
gcc minhttp.c -o minhttp ./minhttp
Smaller version to fit in an 80x24 terminal. Still has the same features, but reconfiguring is a little fiddly. You'll need to consult minttp.c to find out what the config variables mean, and the change the -DVAR=foo as desired. There are no documentation comments in this version and it requires a trickier set of compiler flags to make it compile.
Luckily, the program is also a valid shell script which will correctly compile itself and then run.