how to setup Mass Virtual Host using VirtualDocumentRoot on Snow Leopard
You need to update you httpd-vhosts.conf to something like this:

&lt;VirtualHost *:80&gt;
    DocumentRoot "/Users/me/Sites/www.site1.dev"
    ServerName www.site1.dev
&lt;/VirtualHost&gt;
&lt;VirtualHost *:80&gt;
    DocumentRoot "/Users/me/Sites/www.site2.dev"
    ServerName www.site2.dev
&lt;/VirtualHost&gt;


Having each domain separately in your config allows you to have separate server options for each, e.g. Rewrite config, separate log files, etc.

Then, update your /etc/hosts and add this at the end:

127.0.0.1   www.site1.dev
127.0.0.1   www.site2.dev


This step is particurarily important as this is where your OS looks first when resolving domain names. Otherwise it will not know what www.site1.dev is.

Then simply restart the server by disabling Web Sharing and enabling it again.

To make sure your config works you can check apache logs (access_log and error_log) via Console.app (Files > /private/var/log > apache2).