Quick’n dirty shell script to serve a single file over HTTP:

#!/bin/sh

trap 'echo stop; exit' SIGHUP SIGINT SIGTERM

while true
do
    (echo -e "HTTP/1.1 200 OK\r\nContent-Type: text/html\r\n\r"; cat $*) | \
        nc -l 8000 > /dev/null
done

You’ll need netcat (nc) to run it, it will listen on port 8000.