If you're writing some type of article or blog post that's displaying code, a syntax highlighter can be very useful. I searched through Drupal's modules and found a few, Syntax Highlighter, GeSHi Filter and JavaScript Syntax Highlighter. Both the "Syntax Highlighter" and "JavaScript Syntax Highlighter" are written in JavaScript, the code highlighting is handled by the browser.

Has a client ever asked if you could reorder or change the name of a tab. Instead of displaying the view, edit and revisions tabs, the client wants to move "revisions" before “edit” and rename "view" to "current". This can all be archived by writing a custom module and implementing hook_menu_alter, but there is a module that allows site builders to rename, reorder, disable and hide tabs. It’s called Tab Tamer.

Drupal's multi-site capability has been around for quite some time. Site builders are able to spin up multiple sites, using the same code base, by creating a folder in the sites directory that matches the host name and path. On a production server the URLs never change, but if you want to create a local development version of your multi-site setup that’s where things get complicated.