I've used this thing once to upload some software to my Macbook Air and to be honest I don't need it. It's boxed and in as new condition, comes with all the bits and bobs, I bought it about 3 months ago.

Cost £66 new.

More info here: Apple MacBook Air SuperDrive - Apple Store (UK)

Please not it only works with the Macbook Air and later Macmini.

£45 (postage free)