SQL Server 2008 r2: What events/queries hit tempdb
To summarize Tempdb is used to store 3 types of objects:


user objects 


local temporary table (seen by one session)
global temporary table (seen by all sessions)
Table variables 

internal objects used temporarily by SQL server during Query processing : operations such as sort , join, hash and cursors all require space in tempdb. see the sys.dm_db_session_space_usage DMV.
the version store : 
The following features make use of the version store:


Triggers
Snapshot isolation or Read-Commited Snapshot isolation
Online index operations
Multiple Active Result Sets (MARS)



Please note that using the sys.dm_tran_version_store can be ressource intensive.

May I suggest that you check Troubleshooting insufficient disk space in tempdb for a few examples of how to use the DMV.