More Mac 101, our ongoing series of tips for those new to Mac OS X. One of my favorite things to do when I see someone else's Mac is to see what "Menu Extras" they use.
Menu Extras live in the menu bar at the top of your screen, over on the far right-hand side. As you add more third-party software to your Mac, you will probably notice more and more items showing up there.
If you open System Preferences and type "menu bar" you can find 12 different Menu Extras you can "show" in the menu bar, but one of the most popular and useful is the AirPort Menu Extra. In Snow Leopard, the-already-quite-handy AirPort status icon became a lot more powerful and informative. Apple has posted a page explaining the various meanings behind AirPort status icons.
Generally speaking you ought to see only a few of these: an empty icon (AirPort is turned off), grey curved lines (AirPort is on but not connected), or 1-4 black lines indicating signal strength of the Wi-Fi connection. New in Snow Leopard is the "animated" AirPort icon which appears when AirPort is searching for wireless access points or waiting to be assigned an IP address. (If you are seeing a different icon, check out the page from Apple.)
Since we're looking at the menu bar, here's another tip: option-click everything. Several menu extras, especially ones from Apple, have additional features/information which you can access if you hold down the alt/option key while clicking on the icon. Here's what happens when you click vs option-click several menu extras from Apple (several of these are new and/or improved in Snow Leopard):
Volume: a regular click will reveal a slider to adjust the volume but an option-click will show a list of input and output devices to choose from (similar in function to Rogue Amoeba's SoundSource, which was recently updated for 10.6 compatibility).
MobileMe: a regular click shows time of last sync, option to sync now, and option to open the System Preferences panel for MobileMe. However option-click shows a wonderfully detailed list of every item MobileMe knows about, as well as when it last synchronized succesfully. It also offers Sync Diagnostics, Reset Sync Services (something I still have to use far too often, but less frequently than in the past) and a few other options.
Bluetooth: a regular click reveals basic settings and "paired" devices. An option-click adds a "Bluetooth Explorer" and "PacketLogger" (two "pro" options that you may never need, but are helpful for troubleshooting) as well as showing the version number.
AirPort: a regular click will show available networks and a few basic options, but an option-click shows several bits of information about your current Wi-Fi connection; however, most people will probably just be interested in the Channel and Security.
The basic point is this: feel free to option-click around. If the particular menu extra does not have any "hidden features" to show, it will still show the regular options even when you option-click. You won't hurt anything.
Final menu extra tip: if you want to remove a menu extra from the dock, you can try dragging it while holding down the command key. If that doesn't work, look in the application's preferences for an option to show or hide its menu bar item.
Once you have mastered the basics, you may want to explore some more powerful third-party menu bar items.