Best way to create subsites? What's the best way/module I can use to automatically create subsites, like drupalgardens.com.

Is there a module to do it? Can I use drush for this?
If you want something like drupalgardens (aka new sites), you can use drush site-install, but you will still need to create the site directory and what not.

If you have a basic template for the new sites you should probably create an install profile or feature module and have it set everything up.