There are two major trinket lists on Shadowpriest.com at the moment:
http://shadowpriest.com/viewtopic.php?p=241622#p241634 - Trinket info is outdated.
http://shadowpriest.com/viewtopic.php?f=73&t=30329 - Is more helpful.
I did a long list of testing the top five competing trinkets in different combination's and found the second list to be mostly in line with the results. Dark Moon Card: Volcano is your best in slot trinket by far.