"Rules Set Site Variables” allows you to use the power of Rules to change site configuration and site variables. Create a rule or rules action and then add the action Set Drupal Site variable. You can configure which site variable you want to modify and text you want to change or modify.
The Rules block visibility module allows Rules components to be used to control block visibility. This provides Drupal administrators and developers extreme flexibility in controlling when blocks should be displayed on their websites, in addition to the default visibility options provided by Drupal.