Address and Contact Info
Address: Cornish El Nile- Ramlet Boulac Cairo, Egypt ZIP Code: 11638 PO Box: P.O. Box N° 8 - Sabttiya
Principal contacts for the collection:
Hours and Usage Restrictions
The Manuscripts room closes at 3pm (although they tend to kick you at at 2:30pm). I believe that the other libraries are open until 7 or 8pm.
Online Catalogs and Finding Aids
It's not online, but there are catalogues of some of the Manuscripts (some available only in Arabic).
UNESCO has digitized pages from select manuscripts here: 
--- Dār al-Kutub al-Miṣrīyah. دار الكتب المصرية. Nashrat Dār al-Kutub al-Miṣrīyah tashmulu al-kutub allatī iqtanat́hā al-Dār. نشرة دار الكتب المصرية تشمل الكتب التي اقتنتها الدار. Published al-Qāhirah : Dār al-Kutub al-Miṣrīyah, 1949- القاهرة ، دار الكتب المصرية, 1949- .
--- Dār al-Kutub al-Miṣrīyah. دار الكتب المصرية. Fihrist al-makhṭūṭāt. فهرست المخطوطات. Published [Cairo] : Maṭbaʻat Dār al-Kutub al-Miṣrīyah, Qism Ḥimāyat al-Turāth, 1956. [ القاهرة ] : مطبعة دارالكتب المصرية, قسم حماية التراث 1956.
---Nicol, Norman D. Catalog of the Islamic coins, glass weights, dies, and medals in the Egyptian National Library, Cairo / by Norman D. Nicol, Raafat el-Nabarawy, Jere L. Bacharach. Published Malibu, CA : Undena Publications, 1982.
---Dār al-Kutub al-Miṣrīyah. Arabic papyri in the Egyptian library / by Adolf Grohmann Published Cairo : Egyptian Library Press, 1934-
Arabic Newspaper and other periodicals from Egypt and rest of Arab World (2nd floor). Phonograph records and music from 19th and 20th century Egypt (3rd floor) Rare books mainly in Arabic (5th floor). Manuscripts (3rd Floor).
I have heard that there is also a papyri collection.
Suggestions for approaching the material: Patience is required. There are catalogues, but they're difficult to use. The computerized catalogues in the manuscript room are less reliable than the card catalogue and the catalogues in books.
Housing and getting by for less in the area: The Dar al-Kutub is on the Corniche on the downtown side. There are minibuses from Maidan Tahrir (accessible by metro) but, if you're anywhere in central Cairo, it's not expensive to take a cab. If the cab driver doesn't know the Dar al-Kutub (many do), the Conrad Hotel is next door and most drivers know that.