Apache virtualhost - Mac OSX 10.7.3
There could be multiple causes to this issue.

First, have you tried restarting Apache?
You can do so by typing sudo apachectl graceful in the Terminal.

If that doesn't work out, try to create a folder in the predestined folder (Sites), and see if it works. Alsoo, make sure you've enabled the proper settings: 


And just for the record, my httpd-vhosts.conf file (on a Windows though) looks like this:

NameVirtualHost *:80

&lt;VirtualHost *:80&gt;
    ServerName dev.test.be
    ErrorLog "logs/test.log"
    CustomLog "logs/test.log" common
    DocumentRoot "C:\Users\me\workspace\test\drupal"
&lt;/VirtualHost&gt;