Menu Extras are those menus that appear at the right side of your menu bar (typically with icons).

You can rearrange them by command-clicking on one and dragging it left or right. Remove them like Dock items: Command-Drag away from the menu, let go and poof!

MenuExtras included with OS X are:

• volume,
• the clock (enhancement for this: http://www.scriptsoftware.com/iclock/ )
• battery indicator,
• AirPort indicator,
• Displays menu
• the Connection menu (see NetworkPreferences).
• iSync menu (iSync 1.0 web release)

Set any of these to display in the related SystemPreferences panel.

A few available from places other than Apple: ClassicSpy, ProcessWizard, MoonMenu, LaunchBar, ...

1 Advanced Hacking

There is a complex hack to change the colour of these icons: http://www.resexcellence.com/hack_html_02/07-30-02.shtml

Bscially, these are kept in /System/Library/CoreServices/Menu Extras

You can access the PackageContents and replace the icon files with colourized verisons of the same. (or replace them with something totally different!)