50 Connect.co.uk has an article up, Major Jewish Genealogical database with over 50,000 records from Istanbul, Turkey, that covers, well, 50,000 Jewish genealogical records.
According to the article:
The material covers the period from 1870 to the present. The new online-accessible collection includes over 50,000 records, including more than 35 thousand Istanbul marriage records and some 15,000 death and burial records from other sources including the Chief Rabbinate of Turkey and the Ashkenazi and Italian community records.
You can view the new (or rather old) records at the Instanbul Jewish Genealogy Project