Hack Your Laptop with Sleeves, Skins, Stickers and a Custom Paintjob!

My favourite is iToppers Custom which allows you to send in your own design or photo and they send you a sticker which you can stick to the top of your Mac laptop.

visit the link below for more pictures of laptop skins sleeves, and stickers:
http://www.smashingmagazine.com/2008/03/17/laptop-sleeves-skins-and-stickers/

For a more extreme overhaul of your Mac laptop, why not custom paint it? Look at this website for example of Colorware Pc's custom colored Macbook Air:
http://www.colorwarepc.com/p-126-macbook-air.aspx