This module can make the admin_menu a different color for each environment. Also integrates with Toolbar module (core) and it also works on it's own. :) -Jeff

From the module page, "Colorbox is a light-weight customizable lightbox plugin for jQuery."

There are other modules, like Lightbox2, but lately, most people are going with Colorbox, it seems.

Make all external links open in a new window. There are optional custom exclude/include filters.