The first stop in looking for archival information is to check a guide to the archives for your particular region.
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
http://tinyurl.com/d4ouevm
and
Repository of Primary Sources
http://webpages.uidaho.edu/special-collections/other.repositories.html
Both of these sites have links to archives all over the world. Both have access primarily through a geographic index. The UNESCO portal has additional materials that can be helpful if you are seeking government regulations regarding archives.
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 at left.
Please notice: Effective January 1, 2015, the list of Repositories of Primary Sources will no longer be updated or maintained.
International Council on Archives hosts members from all nations of the Balkans. Individual member countries, with their participation in ICA activities, are searchable from this site. You can acces this site here.