I really wish I had the entire Verfasserlexikon as an electronic database. The only problem is that it doesn't yet exist (except as a shadowy scanned version rumored to exist among doctoral students of Germanistik in Germany).
Barring that, I really wish I had the entire Verfasserlexikon sitting on my bookshelf, or at least in the library. The only problem is that all the volumes and indices together cost thousands of dollars. (I do recommend the reasonably priced one-volume Studienauswahl, however. The paperback 11-volume Studienausgabe is attractively priced, but still a significant investment.)
So for tracking down manuscripts, secondary literature, and links to archival descriptions and digitized images, the first place I check is handschriftencensus.de, which combines the Marburger Reportorium (for 13th-14th century manuscripts) and the Paderborner Reportorium (8th-12th centuries).
My own, indirect contributions are here, here, here, here, here, and here.