Wowhead.com has a most excellent feature that I think few of us use to its fullest extent.
If you click on “Database > Items > Armor”, you can choose ‘Priest’ and then ‘Discipline’ (or whatever) from the dropdown menu titled “Start Weighting… Preset:”.
Doing this gives you a list of all gear for Discipline Priests in one huge list (I’d recommend limiting the required level or iLevel – 333 or higher if you want to run Heroics).
In the results, off to the right, there’s a ‘Score’ that shows how good it is for the spec you selected in ‘Presets’.
The down side is that it doesn’t have any commentary, but for pure numbers and names, it can’t be beat.