Drush is an amazing tool for managing nearly all aspects of a Drupal site and my latest trick is using Drush to pull in all of my favorite modules for a new build. There are plenty of ways to get modules downloaded to a project, but Drush's make command is a clean and powerful tool for the job.
When you've got a site with any sizable amount of content, sometimes you'll just want to do a bunch of things to a bunch of stuff. The Views Bulk Operations module provides a powerful extension to Views that allows you to do just this. Awesome stuff.
When you need Drupal to do more stuff, the general course of action is to first peruse Drupal.org to find a module that suits your needs. How do you know which ones are safe to install and which ones will suit your needs?