gistfile1.rb

module Instantizable
  def instantize(name)
    klass = self
    define_method(name) do |*args, &block|
      klass.send(name, self, *args, &block)
    end
  end
end

# Test the module with a normal method, a method with a hash arg, and a method with a block.

module ModuleOne
  extend Instantizable

  def self.caps_reverse(obj)
    obj.reverse.upcase
  end
  instantize :caps_reverse
end

raise if ModuleOne.caps_reverse("string") !=
         "string".extend(ModuleOne).caps_reverse

module ModuleTwo
  extend Instantizable

  def self.yield_and_upcase(obj)
    yield(obj).upcase
  end
  instantize :yield_and_upcase
end

raise if ModuleTwo.yield_and_upcase("string") { |str| str + 'more_stuff' } !=
         "string".extend(ModuleTwo).yield_and_upcase { |str| str + 'more_stuff' }

module ModuleThree
  extend Instantizable

  def self.extract_a(obj)
    obj[:a]
  end
  instantize :extract_a
end

raise if ModuleThree.extract_a(:a => 1, :b => 2) !=
         ({:a => 1, :b => 2}).extend(ModuleThree).extract_a

Why not using this?
So you don't need to open the Module class (as you've just shown me on irc btw ;)).

module MyModule
  def self.caps_reverse str
    str.upcase.reverse
  end

  def caps_reverse
    MyModule.caps_reverse self
  end
end

MyModule.caps_reverse "blah" # => "HALB"
"blah".extend(MyModule).caps_reverse # => "HALB"