Note: Not all sites are federal or international government-sponsored

Treaties

International Treaties
Extensive list of links from the New York University School of Law Library

United Nations Treaty Collection

Multilateral Project
From Tufts University, this site collects multilateral agreements and accompanying treaties

Selected International Treaties and Agreements
From the US State Department.

Law Library of Congress: Treaties
Links to a variety of sources on treaties, multilaterals and special-focus treaties.

International Intellectual Property Documents
From the US Patent Office, this site include the "Patent Cooperation Treaty"

Constitutions

Constitution Finder
Constitutions of over 200 nations with accompanying charters and other related materials in the native language and English translations. Some historical materials are also available.

World Constitutions and International Treaties
From Texas A&M University, this like other sites is not comprehensive due to the difficulty of locating this material. Links to other sources provided for further searching.

World Factbook (CIA)
While not providing a link to the text, this page does list the date of the most recent revision or adoption.

General

Country Studies from the Library of Congress
While not providing access to constitution texts, there is useful information on the historical development of the nation's current constitution and treaties.