Hosted by the American Mathematical Society, the aim of the AMS Digital Mathematics Registry "is to provide centralized access to collections of digitized publications in the mathematical sciences" and related areas like computer science. This includes both journals and journal-like book series. The resource list can be sorted by title or source (publisher). For every title listed, there's an indication whether it is open access, a subscription is needed, or it is a combination of both. Many of these resources predate the 1940 starting date for MathSciNet (Mathematical Reviews), but are now covered in MathSciNet.
Based on a section in "The Digital Mathematics Library" by Allyn Jackson, appearing the Notices of the AMS 50 (8) 2003, this site lists retrodigitzed journals and books. The list may be sorted by journal, repository, title, or author.
Defining open access journals as “journals that use a funding model that does not charge the readers or their institution for access,” the DOAJ aims to be a comprehensive listing of open access scholarly journals that use a quality control system to guarantee the content. Journals can be located by title or broad subject.
This Web site, sponsored by the European Mathematical Information Service (EMIS), provides a listing of open access mathematics journals.
Created by a consortium, EuDML is an open access collection of journal articles, books, and multivolume works published in Europe. Over half of the collection is in English, however, other European languages are represented. There are basic and advanced search capabilities, and browse by subject and browse by journal features. The earliest publication is from 1584.
European Libraries Electronic Resources (EULER) in mathematical sciences provides searching capability to find resources such as books, pre-prints, Web sites, abstracts, proceedings, serials, technical reports, and thesis.
Math-Net.Ru contains a collection of mathematics journals in the original Russian language. There are also a few physics, computer science, and engineering journals. Most of the journals are published by the Russian Academy of Sciences or a Russian institute or university. There is a three year embargo for many of the journals, however, a few have shorter embargoes and some provide completely free access.