I've bought the Kensington PocketMouse Pro with a retractable cord that retracts fully into the mouse. Great for mobile workers. Its small and takes up less power from your laptop than any bluetooth mouse. Turning bluetooth off prolongs battery life.
I've also got a 80gb super slim/small external hard disk from eBay.
Radtech also produces some neat accessories for Apple laptops.
Marware's Protection Pack for Macbooks which consists of a wrist rest and keyboard cover. The wrist rest is a slip of PVC leather designed to prevent scratches and provide a smooth, padded work surface. The non-permanent special adhesive allows for effortless complete and clean removal. The dual-purpose Keyboard Cover is made of microfiber, the same material used for lens cloths. Perfect for protection against impurity transfer and for use as a screen cleaner.
I'm just waiting for someone to release a airplane power adaptor for my macbook which unfortunately has a magsafe tip.
Hope this info is useful.
Regards
Darryl