Strcmp is a simple ruby gem that is used to compute how similar two strings are to one another. It includes a fast C implementation of the [jaro-winkler] (http://en.wikipedia.org/wiki/Jaro%E2%80%93Winkler_distance) distance algorithm and soon the levenshtein distance algorithm. More metrics on the way. I claim no ownership of the algorithm.
gem install strcmp
Using the gem is simple. First add the require statement to the file you wish to use it in.
require 'strcmp'
To use the gem call:
StrCmp.jaro_winkler("martha", "marhta") => 0.961111
StrCmp.jaro("martha", "marhta") => 0.944444