The Character Palette (pictured in full after the jump) is one of my favorite little bits of Mac OS X that often goes overlooked. Any character embedded in any of the fonts installed in your computer is accessible via this little menu system. With it, you can add special symbols to any word processor you are running or whatever program you may have running in the forefront. As you can see, I've added the unicode telephone symbol to my iChat status menu. The only downside to this is that it won't display properly in chat clients that cannot handle unicode (which means nearly everyone running Windows).
You can activate the Character Palette by navigating to System Preferences—>International, click on the Input Menu, and make sure that there is a check mark next to the Character Palette. The result will be a flag representing your keyboard layout in the menu bar; click on this and select Show Character Palette to launch it whenever you like. Read more after the jump...
You can leave the Character Palette running and simply call it to the front whenever you need to add a new character / special symbol. Simply highlight the symbol you wish to use and click the Insert button to add the symbol to the foremost text field. You can also click the little sprocket menu icon in the lower left corner of the Character Palette and select "Add to Favorites" to add the selected symbol to your favorites. Now you can keep all your hard to find symbols in the Favorites pane of the Character Palette. Enjoy!