The American Society of International Law produces, and updates on a 6-monthly basis, the excellent Guide to Electronic Resources for International Law. Chapter contents include human rights, the EU, international criminal law, private and public international law, intellectual property and the UN.
Within each chapter, the authors set out strategies on how to find international legal materials, as well as providing links to both primary and secondary material available online.
The Society, in collaboration with the Andrew W. Mellon foundation, has also developed EISIL (the Electronic Information System for International Law), a searchable database with links to quality international law information on the Web. I've carried out a couple of searches and found some useful results, so if you're studying subjects with an international dimension I'd recommend giving this a go.