A list of (respectable) open access journals in mathematics: https://thehighergeometer.wordpress.com/2019/01/13/some-serious-open-access-journals-in-mathematics/
Possibly because it's aimed more at math than CS, it doesn't include the two open journals I read and write to most frequently, J. Graph Algorithms (http://jgaa.info/) and J. Comput. Geom. (http://jocg.org/index.php/jocg).
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