Even has posted a great guide on BlackBerryforums on how to clean your BlackBerry trackball. This may interest many users including me since mine is already black from dirt and grime. The guide requires you to get down and dirty with your device with a screwdriver and a “spudger” (not sure what that is) so this may not be for the faint of heart.
Personally I actually like the feel of the trackball better when it is dirty since it gives better feedback . If your crazy about cleanliness or just want your device to look like new check out his guide at this link. You do need a few tools to get the job done but nothing major. Keep in mind if you ruin anything this will most definitely void your warranty. Thanks Even!