This script encorporates best practices in securing file permissions
for Drupal outlined here: http://drupal.org/node/244924

The script performs some checks before any modification to ensure it is not applied on files/directories outside your drupal installation.

Run the script as follows: 
"sudo bash fix-permissions.sh your/drupal/path your_user_name"

Note: The server group name is assumed "www-data", if it differs modify it in the script code