sp_depends lists the triggers that reference an object, or all the tables or views that the trigger affects.

This example shows how to use sp_depends to get a list of all the objects referenced by the trigger deltitle:
sp_depends deltitle 
Things the object references in the current database. 
object              type       updated  selected 
----------------    ----------  ------- -------- 
dbo.salesdetail     user table  no      no
dbo.titles          user table  no      no
(return status = 0)

This statement lists all the objects that reference the salesdetail table:

sp_depends salesdetail 
Things inside the current database that reference the object.
object                       type         
---------------------------  ----------------  
dbo.deltitle                 trigger         
dbo.history_proc             stored procedure  
dbo.insert_salesdetail_proc  stored procedure
dbo.totalsales_trig          trigger 
(return status = 0)