TechShop:Creating graphics for a CD
You can print directly onto cd's using printable cd/dvd media and an adapter for a number of consumer printers, this normally comes with its own 'design' software. A number of print houses will print onto a run of cd/dvd media for you, however you will need to provide the correct documents to a standard template. You can also print onto Labels that you can use in laser printers (like the ones at WSA) using templates to ensure that the image is printed into the right location.
Standard CD sleeves are 12x12cm however there are a number of styles. Please see the links section for links to templates you can use in Illustrator and Photoshop.
There is also a technology called lightscribe that allows you to use the laser in a cd/dvd drive to create patterns onto 'normal' cd/dvd disks