Snagged from http://www.rubyquiz.com/quiz113.html

# be sure to use sort_by rather than sort
quiz = (1..10).to_a
quiz.sort_by { rand }

class Array; def sum; inject( nil ) { |sum,x| sum ? sum+x : x }; end; end

It's class agnostic, so you can do this:

[1,2,3].sum              # => 6
['a','b','c'].sum        # => 'abc'
[['a'], ['b','c']].sum   # => ['a', 'b', 'c']

You can then add a 'mean' operator easily:

class Array; def mean; sum / size; end; end

mean only works for numbers though, of course, like so:

[1,2,1000].mean    # => 334

That said, if your class implements division, it'll also work!

Checks to see if a string is actually the serialized version of an array. If it is, we return an unserialized version. If not, return the original string. This way, we can just call our function on stored DB values and not worry about checking the results.

This was snagged from the Wordpress 2.0 source. Yayyy for Open Source!

	function maybe_unserialize ( $original ) {
		if ( false !== $gm = @ unserialize($original) )
			return $gm;
		else
			return $original;
	}

class Array
    def swap!(a,b)
         self[a], self[b] = self[b], self[a]
    self
    end
end

You can now do stuff like..

[1,2,3,4].swap!(2,3)  # = [1,2,4,3] etc..

Many thanks to Sam Stephenson and technoweenie for their suggestions.