You can add custom columns to the Site Settings page by adding a CustomActionGroup. Very useful when combined with CustomAction elements since you can create your own management shortcuts.
Try adding a feature with an element manifest that contains this:
<CustomActionGroup Id=”MyCustomColumn”
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Posted under Developer

You can create more elaborate CustomAction elements by letting an assembly and a class handle the creation of the CustomAction. To do so, set the ControlAssembly and ControlClass of the CustomAction element. You can also use a .ascx user control by setting the ControlSrc attribute.
For example, you can add a menu tree to the [...]

Posted under Developer

Did you know you can add items to menus and lists in SharePoint by creating a CustomAction element in a feature? Try adding a feature with an element manifest containing this:
<CustomAction Id=”CurrentUsers”
GroupId=”SiteActions”
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Posted under Developer