EDIT: The script below has been updated to work with Drush 3.x. Those using previous versions of Drush will need to edit the script appropriately. The nature of the change was to use the new Drush 3.x standard of no spaces with command names, so "drush sql dump" was changes to drush sql-dump."
Before using this script, make sure that all your contributed themes and modules are somewhere in the "sites/" directory. If they are in any other Drupal core directories, your modules and themes will be lost.
I run a handful of small Drupal sites that I can't afford to spend too much maintenance time on, but that still need to be updated with the occasional maintenance version of Drupal.
It can be quite time-consuming to manually update 4 or 5 sites each time a security release is published.
So, a couple months ago I spent an afternoon writing a shell script to automate the whole task. With a little help from Drush, it turns a 10 or 15 minute maintenance task into about 10 or 15 seconds.
Here's what it looks like.