For simple web-based services I usually just use Perl and CGI.pm. After having read a bit about HTTP::Engine I tried it for a simple project yesterday. Beside my own logic it only took a few line of code to have a stand alone HTTP server for my service.
My colleague needed it to be served from the same Apache server as the rest of his webapplication. Some tiny changes and my stand alone server was transformed into a plain CGI script. When we going to deploy the script I’m guessing we make some tiny changes and have it running as a mod_perl module.
Try it for you next project! Even if you usually just use CGI.pm.