UN Treaty Collection website is a great starting point. It includes:
Large legal database containing UK, EU and international case law, legislation (up-to-date, amended versions), legal journals, commentary texts, current awareness, and news. Very good range of practitioner texts in the Commentary section including Butterworths Company Law Handbook and Butterworths Family Law Service. Includes All England Law Reports, Encyclopaedia of Forms and Precedents, and Halsbury's Laws.
Westlaw International is a vast global legal research library built on some of the world's best legal, news and business information.
Key legal history research tool. More than 100 million pages of legal history available in an online, fully-searchable, image-based format. Includes:
International Criminal Court (ICC) Legal Tools the ICC Legal Tools project website provides free and immediate access to a wealth of information on international criminal law and justice. The project holds the potential to be the leading information provider in the area of international criminal law.
EISIL electronic Information System for International Law. Developed by the American Society of International Law (ASIL).
Australasian Legal Information Institute includes full text of some cases from various Australian courts and Australian legislation.
Access to Justice Network canadian justice and legal information and services.
Wits Law School the School of Law from the University of Witwatersrand, Johannesburg, SA. Provides information about the Constitutional Court of SA (including an archive of all decisions of the court) and South African legal materials and links.
FindLaw offers various features for the lawyer and non-lawyer (does have an American bias). FindLaw index is quite extensive, visitors can search FindLaw as well as search the full text of law reviews online. The new LawCrawler searches the contents of legal sites on the Internet and can be limited by country.
Google Scholar click on the "Legal opinions and journals" radio button. This enables people to find and read full text legal opinions from U.S. federal and state district, appellate and supreme courts using Google Scholar. You can find these opinions by searching for cases or by topics or other queries.
OSCOLA 2006: citing international law section: The 4th ed of OSCOLA does not cover International Law, so check this guide.