The easiest way to do that is to name your folders with a symbol as the first letter in the file or folder name: like a space, an underscore ( _ ), or a tilde ( ~ ). Mac OS X determines the order of these special characters using your language settings in the International pane in System Preferences.
The names of files and folders in Mac OS X can use almost any character out of thousands of Unicode characters, which include symbols, arrows, and icons as well. There are only two characters you can't use: one is the colon (because it's used by the system). You also can't usually use periods (or full stops) as the first character in a file name (because they're reserved for hidden files).
Also, as far as Mac OS X is concerned, the folder name "AARON" is the same as the folder name "Aaron" (or "aaron" for that matter): this is called case insensitivity. Mac OS X filenames are considered case insensitive.
After the jump, a list of 112 common, easy-to-type characters, and how they're sorted by Mac OS X for English.