I was just encountered with the need to have a multi-site drupal install which utilized a specific theme for each site. In a lot of cases, multi-sites are set up on one drupal install, but utilize individual databases for each site. This is done by setting $db_url in settings.php to point to the database to be used for each site.

In our case, we needed to have a multi-site platform on one drupal install using only one database, but each site needed to display its own theme. This is accomplished by modifying each settings.php file for each site and un-commenting the following code.  read more »