Just came across this yesterday. If you are a TechNet subscriber, changes to the online site have been made which makes organising your subscription much easier through the introduction of the TechNet indexes. You can find this at http://www.microsoft.com/technet/index.
In this Septembers shipment, you get an offline version of the indexes. The index allows you to easily search for products in the subscription to locate which disc it is on by Full Text, by disc number or by part number.