Yearbook of the United Nations (1946-)
Supports searching in:
UN legal yearbooks (including Yearbook of the International Law Commission);
Repertoire of Practice of the Security Council;
and Repertory of Practice of United Nations Organs.
HeinOnline's United Nations Law Collection
Includes many U.N. yearbooks.
Foreign and International Law Resources Database includes:
Older digests of U.S. practice in international law
Some international law year books
International documents reprinted in International Legal Materials (I.L.M.).
(Access subscription HeinOnline databases on campus, in BLS housing, and elsewhere off campus if one has implemented the proxy server instructions.)
Avalon Project of Yale Law School Lillian Goldman Law Library
Contains historical legal and diplomatic documents. Provides full-text of some documents mentioned in international law digests.