TABLE 1: Stored Procedures' Functions
Stored Procedure Function
sp_addlinkedsrvlogin Creates a new SQL Server login mapping for a linked server
sp_droplinkedsrvlogin Removes an existing SQL Server login mapping to a linked server
sp_addlinkedserver Creates a linked server for use with distributed queries and OLE DB data sources
sp_droplinkedserver Deletes a linked server used with distributed queries
sp_linkedservers Returns the list of linked servers defined in the local server
sp_catalogs Returns the list of catalogs in the named linked server
sysoledbusers Contains one row for each user and password mapping for the specified linked server. It's not really a command, but it does have some handy information.