Enable Web Sharing in System Preferences > Sharing. (No need to do this in Mountain Lion. You may need to run sudo apachectl start, though.)
Edit these files:
/etc/apache2/httpd.conf/etc/hosts/etc/apache2/users/your-username.conf- In Mountain Lion, you'll need to copy
Guest.confto[your-username].conf. Also, be sure to change the first line to be `` and then also create the~/Sitesfolder (which will, magically, still have the correct folder icon with the compass on it).