You can use sp_lock (and sp_lock2), but in SQL Server 2005 onwards this is being deprecated in favour of querying sys.dm_tran_locks:
select
object_name(p.object_id) as TableName,
resource_type, resource_description
from
sys.dm_tran_locks l
join sys.partitions p on l.resource_associated_entity_id = p.hobt_id