This book, by one of the leading scholars of the ICJ, offers an excellent introduction to the court.
The ICJ site has an excellent collection of pleadings and memorials.
You can also find ICJ pleadings and memorials in print at USF's Zief Library by searching Ignacio using the "Doncore" box or searching by Keyword. For either method, include the phrase "Pleadings, oral arguments, documents" in your search. (Be sure to include the quotation marks.)
Use these online, print, and microfiche sources to find decisions of the Permanent Court of International Justice. The work of this predecessor to the ICJ spanned the years 1922 to 1945/46.
These sources collect decisions of national courts on international law, and sometimes include selected decisions of international tribunals and courts.