Using sys.dm_os_wait_stats I have identified what I believe is a locking problem

  wait type    waittime  pct     running ptc
  LCK_M_RS_S   2238.54   22.14   22.14
  LCK_M_S      1980.59   19.59   41.73

Is there a way I can find the top blocking/locking queries? I've tried querying sys.dm_db_index_operational_stats without much luck.

sql-server sql-server-2005 sql-server-2008 query-optimization
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