The Levenshtein distance is a string metric for measuring the difference between two sequences.

http://en.wikipedia.org/wiki/Levenshtein_distance

For #ruby you can use #gem levenshtein-ffi and do something like this:

class Organization < ActiveRecord::Base
  def self.find_similar(name)
    all.find_all do |org|
      Levenshtein.distance(name, org.name) < [name.size / 3.0, 3].max
    end
  end
end

And help your users to prevent mistakes of typing.