This is a very simple and basically useless "hack", but it's novel and I like it.
This causes any Windows machine that you plug your Kindle in to to display an icon for the drive. You can see it in the screenshots below:
This is very easy to install. Just download the zip and copy autorun.inf and kindle.ico to the user store. To see it, unmount the Kindle and plug it back in. If you want to get rid of it, just delete the two files.
You can change what icon is shown in autorun.inf. I've included two icons, the one in the screenshot and this:
but in 48x48.
To change what icon is used, just open autorun.inf and change the second line to the filename of the icon. You can even use your own icon. I recommend making it 48 by 48 pixels and with transparency.
You can hide the files by right-clicking them, clicking Properties, and checking the "Hidden" box. If you don't have hidden files and folders enabled, they should disappear. You'll need to enable viewing of hidden files and folders to see them again.