The first stop in looking for archival information is to check a guide to the archives for your particular region. For Russia, Ukraine and the Baltic region, the very excellent English language, printed guides by Patricia Grimsted are a great, if now somewhat dated, beginning. The Russian guides by Grimsted are the most up to date published sources. In this area it is probably most useful to look at online guides. These tend to be the most current and are readily accessible through the archival portals maintained by the University of Idaho or UNESCO.

Directories 

The directories listed here index points of entry for archives all over the world.  The wealth of online material can save a great deal of time when planning a research trip that will include visits to regional archives.  Most of the sites that are listed in these directories have, at the very least, citations to published archival guides.  Many have online finding aids.  Two of the most important general directories for archives are:

UNESCO Archive Portal

and 

Repository of Primary Sources

Both of these sites have links to archives all over the world.  Both have access primarily through a georgraphic index.  The UNESCO portal has additional materials that can be helpful if you are seeking government regulations regarding archives. Please note that there have been some changes made to the site that are described in more detail under the Guides tab of this Libguide.

While both of these sites have numerous links to regional archives they are not comprehensive.  When looking for regional archives it is often useful to start at the national archival site for a particular country.  Most have a page of links for regional archives, some drop-down lists.  Links to many of the national archival sites for the area are listed below.  

National Guides

ArcheoBiblioBase
http://www.iisg.nl/~abb/index.php

This site grew out of the work of Patricia Kennedy Grimsted and her vast knowledge of the Russian Archives.  Dr. Grimsted developed English language guides to the Russian archives many years ago and began extending those guides to an electronic format some twenty years ago. 

Along with the mailing address and email, there is a link to the archive's website whenever possible.  Information on the archives' facilities are also available here for each archive.  This format builds on Grimsted's original printed guides.  The site also includes links to the citations of reference materials.

Today the English version of the guide resides at the International Institute of Social History in the Netherlands.  Within the subfiles of the website the scholar will find information about and links to archives.

 Archival guides are also listed in historical and other subject bibliographies. If you are trying to identify the most current guide it is often helpful to consult the website for the archive. When the archive does not have a website the historical or library science bibliographies are often the only alternative.

Finding published tools specific to an archive is often most easily accomplished today by looking at a particular archives website.  Identifying the published guides can be tedious.  They were usually included in historical bibliographies, but these are often annual publications so finding all the guides to an archive would mean searching all the volumes of the bibliography.

The national archival sites for individual countries have made this process much simpler.  Each addresses the issue in its own way. Some, like the Hungarian National archive, include links that allow the user to access lists of the published finding aids available for the archive.  For example, the website for Czech archives has a link in the upper-left of the webpage to the search aid for Czech repositories.  The search interface is available in a number of languages including English.  A very simple search for the term "ruske" brought up numerous matches.  The entries are extremely useful as can be seen from the sample below.

Note that the entry includes a reference to a published finding aid.

The Bulgarian National archive portal includes a link to a listing of information for the regional archives.  Each link includes subdivisions devoted to specific topics including lists of published guides to each of the archives.