FixPhrase.com uses an open source, patent-free algorithm to convert latitude and longitude into a set of four words from a word list. Those four words (a FixPhrase) can be put back into the algorithm to get the original latitude and longitude.
FixPhrases can be shorter than four words too if less accuracy is required. The first two words will locate a city, the first three words will locate a neighborhood, and all four words will locate the corner of a house, the pitcher's mound in a baseball field, or six adjoining parking spots.
The master word list is ordered alphabetically, and each word in a FixPhrase is taken from a different area of the word list. This means the words in a FixPhrase can be entered in any order but will always translate to the same location.
Because the word list is alphabetized, it's easy to see if two FixPhrases are located near each other. The first two words will usually be the same, and the third words will either be the same or will start with the same letters.