Over the past couple years Drush has become an essential part of the Drupal site builder's toolkit. I personally use it daily and like a lot of developers now couldn't imagine building a site without it! (Well, I suppose I could imagine it, but I can also imagine building sites in Drupal 4.6, and it's not pretty ;) ).
Drush is one of those areas of Drupal that has been very well documented and I think it would be useful to compile what I feel are some of the more appropriate areas for site builders. There are many awesome webcasts, though I'm personally biased against them due to my forever inconsistent connection speeds while I'm traveling, so don't take it personally if I pass your webcast by :). Most of the existing documentation is written for D6, but fortunately Drush is Drupal version agnostic so all D6 documentation should work almost identically to D7.