There are a few ways of doing this and all basically involve using the reverse proxy or "ProxyPass" feature of Apache to accomplish it.
1.) Create a normal vhost and simply symlink the root directory of the site you want to mirror.
Eg. originalsite.com and newsite.com
/vhosts/originalsite.com/httpdocs
You would symlink like this:
ln -s /vhosts/originalsite.com/httpdocs vhosts/originalsite.com/........
This is useful for developing a lot of applications, I'm putting it here to keep it handy for myself and hopefully others:
Choose CountryCanadaJapanUnited StatesUnited KingdomAfghanistan........