I was looking for a way to clear cache on specific sites as I have a a Drupal Multi-Site setup that has more than one database. Sometimes I only want to clear cache on one database at a time.
Since it took longer than 5 minutes : ) to find advice on this subject, I am posting here in hopes that it will help.
There is a little up-front set up involved but it is worth it when you have a setup with multiple databases.
Drush aliases are a powerful tool to get to know. With Drush aliases, it is possible to run commands on a remote server from your local server. Pretty awesome if you like to save time.
Here is an example for setting up drush aliases:
http://drush.ws/examples/example.aliases.drushrc.php