SharePoint Custom Action Identifiers

http://johnholliday.net/resources/customactions.html

http://blogs.msdn.com/dipper/archive/2006/10/05/How-to-Remove-or-hiding-items-in-List-toolbar-in-Sharepoint-Server-2007.aspx

http://asadewa.wordpress.com/2008/02/23/removing-single-file-upload-menu-from-document-library-toolbar-moss-2007/