Good explanation of the Levenshtein distance: http://www.csse.monash.edu.au/~lloyd/tildeAlgDS/Dynamic/Edit/

And a good implementation: http://stevehanov.ca/blog/index.php?id=114

Very good generic game action framework software engineering discussion here:
http://www.gamedev.net/topic/624995-am-i-over-engineering-a-generalized-game-action-framework/page__view__findpost__p__4940963