National Union Catalog of Manuscripts Collections (NUCMC)
In addition to general information about the NUCMC program and links to basic archival resources, NUCMC provides online access to two key, fundamental resources:

• NUCMC Z39.50 Gateway to the Archival and Mixed Collections (AMC) file in the RLG Union Catalog. This allows users to search more than 700,000 archive and manuscripts cataloging records in the Research Libraries Group (RLG) Union Catalog. The records describe archival and manuscript collections and items in research libraries, museums, state archives, and historical societies located throughout North America and around the world in the RLIN database.
  
• NUCMC Z39.50 Gateway to OCLC MSS Records. This allows users to search more than 300,000 catalog records available in the OCLC bibliographic database describing archival and manuscript collections in public, college and university, and special libraries located throughout North America and around the world.

Archives Canada
Search more than 50,000 descriptions of archival records from the holdings of all provinces and territories, or discover our Canadian heritage through Virtual Exhibits - online stories told with the use of original archival material. It is maintained by the Canadian Council of Archives.

Archon Directory
The ARCHON Directory includes contact details for record repositories in the United Kingdom and also for institutions elsewhere in the world which have substantial collections of manuscripts noted under the indexes to the National Register of Archives.

Archives Hub
This is a national gateway to descriptions of archives in UK universities and colleges, provided by the University Manchester. Features include quick and advanced search options, a list of contributing repositories, a guide to searching in the form of a workbook, an explanation of archival work and archival description, an online "tour" that introduces novice researchers to archival description and working with finding aids, downloadable posters and leaflets, and a section of information for archivists that includes links to a variety of information such as EAD, continuing education opportunities, and more.

Register of Australian Archives and Manuscripts (RAAM)
This easy to use database contains records describing non-government archives held in Australian archival repositories and libraries. In some cases it also includes information about contributing repositories and libraries. Additional information about most of the repositories represented in RAAM is available in The Directory of Archives in Australia.

New Zealand National Register of Archives and Manuscripts /
Te Raarangi Puuranga, Tuhinga Ake o te Motu (NRAM)
A cooperative effort of several New Zealand library and and archival groups, NRAM includes archival collections held in museums, local government bodies, libraries, historical societies, community repositories, and in-house business, educational, religious and sporting archives throughout New Zealand.

International Catalog of Sources (ICOS) for History of Physics and Allied Sciences

Physics History Finding Aids Website (PHFAWS)
ICOS  is a union catalog of manuscript collections, archival records, oral histories, etc. in physics, astronomy, geophysics and related fields.  It currently has around 8,000 records from about 500 repositories.  Some of the collections are also in RLIN or OCLC but many are not. PHFAWS is a collection of 100+ (mostly) EAD finding aids from 14 major science archives.  The Center for History of Physics (which maintains both websites) intends to expand PHFAWS significantly. 

Library of Congress
An elaborate selection of tools for searching LC's holdings.

Archives of the Archives and Archivists Listserv
This is a tool for searching past postings to the largest archival listserv and the only archival listserv international in scope.

• The University of Texas at Austin SAA Student Chapter has a list of more than thirty Listservs about Archives and Related Topics. Moreover, the excellent UT-Austin student site provides detailed instructions on how to subscribe and post messages to a list.

• a directory of manuscripts repositories in the United States
• collection records from the National Union Catalogue of Manuscript Collections (NUCMC)
• and names and subject indexing of over 42,000 collections whose finding aids have been published separately in the microfiche series, National Inventory of Documentary Sources in the United States (NIDS).

Only ArchivesUSA makes all of NUCMC fully searchable in electronic form. It also integrates the NUCMC and NIDS information to provide a single record for each collection, with detailed information drawn from both resources when available. Because this an annual subscription service, only members of the Tulane community can link to ArchivesUSA from this page. To access this very useful resource from your locality, check with your area libraries and archives to discover if they provide this service.