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.
If you've got development workflow where you're frequently switching among environments, it's easy to get confused about which site you're on. Even the best of us are known to have a little oopsie every now and then so before you go changing site configurations or restoring database backups, you better be sure you're not mucking up the live site. Here's a nifty little module to help you keep things straight.
One of the easiest things you can do to give your website a professional appearance is to use the Path module (core) to enable pretty URLs/aliases and the Pathauto module to automatically generate aliases. Sensible alias configurations give your site a nice, polished look as well as make your content search engine friendly by including node (user and taxonomy, too) data in your URLs.