I use this script to create drupal multisite directories when I want to add a new site to a drupal install. 

Usage (as root): mksite [Site Name]... [Path to DrupalDocRoot]...

Currently it:
1) Adds the site to /etc/hosts
2) Creates a symbolic link in /Path/to/DocRoot/VHosts to the specified drupal root
3) Creates a directory in <drupal_root>/sites with sitename.localhost
4) Creates a directory <drupal_root>/sites/<sitename>.localhost/files 
5) and chmods files a+w
6) Copies sites/default/default.settings.php to sites/<sitename>.localhost/settings.php
7) and chmods settings.php a+w

@todo Use sudo better in the script instead of requiring the user to be root.
@todo Extract configuration bits into a ~/.mksite config file. 
@todo Consider not 777 for files

Possible Future Options
`*´'`°¤¸¸.•'•.¸¸¤°´'`*´

* Create a db with the sitename (user with same name? Ask for password?)