One of my favorite resources is Medioevo latino, an annual publication of all things medieval thought. The parent company, SISMEL, has now improved on-line access to that annual, as well as other things it publishes:

The important resources constituted by the well-known SISMEL's repertories (Medioevo latino, the Bibliotheca Scriptorum Latinorum Medii recentiorisque Aevi, the Compendium Auctorum Medii Aevi) and by the prestigious journals published by the Edizioni del Galluzzo are available on line. For information: www.mirabileweb.it  · info@mirabileweb.it.

Probably mostly academic research institutions will opt to subscribe to this service, but it's nice to know that the service is available.