World Treaty Index (WTI) is a new database that aspires to contain every known international agreement of the 20th century by January 2011 -- over 85,000 treaties! At the moment there are about 53,000 agreements.
This new database will eventually allow the user to calculate histograms on the fly, perform combination searches (by topic, country, etc), merge with other datasets (using the Correlates of War codes), and download all or part of the data in a .csv file.
I just did a search for treaties between Argentina and Uruguay and got 63 results between 1945-1990 with citation information where available (this is not a full-text database). The results tell me what type of treaty (bilateral or multilateral), the date of the treaty, the topic, and the title in English. What a resource!
Both the website and topic codes build upon the work of Peter Rohn from the University of Washington who conducted the original WTI collection process in the 1960's and 1970's.
Here is the direct URL to the database:
Feel free to email the creators of this database with any problems and/or suggestions.