The first time I noticed a cool skin on a laptop, it was Jason Bean's bnpositive logo on a skin on his laptop. It makes him stand out in a sea of laptops and is noticeable from across any conference room.
I decided to go design my skin for my MacBookPro and went through some websites before I found one that was simple to use and fully customizable. The site I decided on was Skinit. The interface to design the skin was incredibly simple to use, and you provide the model number of your laptop so that it's sized correctly and even precut around the logo.
The quality of the resulting skin is incredible… it's and it's quite thick and scratch resistant. I get a lot of great remarks on how beautiful it looks and I love the fact that it promotes my brand. My word of caution: be sure to upload a high-resolution image. My skin is a little pixelated, but it works well since it looks a bit artsy. I also added my twitter name so folks could find and follow me quickly.
I'm surprised that I don't see a lot of major brands provide their conference attendees with laptop skins. How cool would it be to walk into a technical conference hall and quickly identify Google, Microsoft and other employees! It's a lot easier than trying to read their company name on a badge hanging around their neck!