A drush site alias file allows you to streamline advanced drush commands and make running them against both local and remote sites a breeze. With a properly configured alias file and an SSH key you can run frequently used commands that have complex options, with a concise easily remembered "alias" on any site. This will help you be far more productive and you will find yourself using drush itself far more often.
This previously recorded webinar is a high-level presentation on the structure and some common features usually found in a site alias file. This knowledge share does not delve into drush setup or explanations of drush commands, but should be a great starter for developers and builders who use drush, and want to become more proficient and take it to the next level.
Additional Resources:
An Inside Look at the Omega Theme | Mediacurrent Blog Post
Maps and Drupal 7 | Mediacurrent Blog Post
Webinar: Services 3.x Module