The Index of Dead Sea Scrolls Manuscripts is a great tool to get some quick info on the mss. And with the image links, it is nothing short of amazing!
But what about the NT? The CNTTS apparatus has a full list, but its nothing compared to what the DSS index offers.
Or what about the LXX? Logos has recently launched there LXX Manuscript Explorer as well as a Hebrew Bible Manuscript Explorer. But I think Accordance could pull this kind of data together easily considering most of the data is already there in various formats (e.g. Gottingen, Cambridge).
I'd love to see a robust index with all the relevant data in one place. Something like the DSS index, but more robust - a full index that could be searched etc.