thttpd is described as 'Simple:' and is an app in the Development category. There are four alternatives to thttpd for a variety of platforms, including Windows, BSD, Linux, Mac and OpenBSD. The best alternative is Apache HTTP Server, which is both free and Open Source. Other great apps like thttpd are nginx (Free, Open Source), KatWeb (Free, Open Source) and Windows Webserver (Free).
nginx [engine x] is a HTTP and reverse proxy server, as well as a mail proxy server written by Igor Sysoev. It has been running for more than five years on many heavily loaded Russian sites including Rambler (RamblerMedia.com).
The Windows Webserver was developed for testing PHP and CGI/FCGI programs under Windows, without installing an Apache or IIS environment. The Webserver is easy to install and comes with buildin PHP 8.0.8 FastCGI support, mod_rewrite and SSL/TLS 1.2.