I find that the Bibliotheque Nationale Francaise (French National Library) in Paris have scanned most of their catalogues in PDF form and made them available for free download. The intention, clearly, is to do the lot. Thus Zotenberg’s catalogue of Syriac and Mandean mss is online, as is the more recent supplement. The catalogues can be found at:
http://www.bnf.fr/pages/zNavigat/frame/catalogues_num.htm
I’ve been browsing through the catalogue of Arabic mss. As one might expect, the contents are mainly derived from Coptic or Maronite texts. But what a treasure! Sadly we need not ask whether other major libraries have done the same.
They are not printed catalogues..