Last Wednesday I gave a quick live demonstration to the Oxford Drupal Users Group at their monthly meeting. It was on "Drush and drush make": it was originally going to be just on the latter but I was able to add a few demonstrations of basic Drush commands to get the party started. And there ain't no party like a drush make party.
The slides, and the code examples for the Drush make part of the talk, are available in a github repository for you to download if you missed it, or if you'd like to learn how to produce and maintain your own makefiles. Given most of our internal work at Torchbox is now based on versioning drush make files rather than large repositories, and submitting patches to d.o so we can reference them in said makefiles, then I can only recommend you start using drush make, and certainly drush on its own, right away.