foo.rb

class Foo
  def Foo.bar
    :bar
  end

  def self.baz
    :baz
  end

  class << self
    def wombat
      :wombat
    end

    def tofurkey
      :tofurkey
    end
  end
end

Foo.bar
#=> :bar

Foo.baz
#=> :baz

Foo.wombat
#=> :wombat

Foo.tofurkey
#=> :tofurkey