I'm writing a content provider, it will be part of my application. What does the "icon" attribute in the element do though?:
http://developer.android.com/guide/topics/manifest/provider-element.html
Where would anyone ever see this icon? Is there a way for users to list all the content providers in the system, and they might see it in this listview perhaps?
From the documentation you linked I guess this icon will show up instead of the app launcher icon if the user is choosing between different content providers. For example: If you create an own content provider for images, the user will see your content provider + all others in a list if he wants to select an image. If you want to show a different icon for the content provider than your launcher icon, you may change it. But normally there is no need to: The content provider will show the application's label and icon by default.
It is available in the APIs, but not currently shown in the UI anywhere. Don't supply it; if not supplied, an icon will be the same as the app's overall icon, so if this is ever used you will still have a reasonable icon for that component.