Open Images project, an initiative from the Netherlands Institute for Sound and Vision. Many of the videos contain Dutch audio., so it's advised to remove the audio when uploading to Wikipedias other than the Dutch Wikipedia.
Beachfront B-Roll - Constantly updated personal blog offering, for free, royalty free HD stock video, High Definition and HDR time lapse clips and HD animated looping backgrounds for any personal, corporate and commercial use. Downloads are a simple "Right Click Save" and the files are hosted by Archive.org.
Videvo Stock Footage Royalty-Free Stock Video Footage CC licensed (BY-3.0) or licensed by the company for easy use in non-commercial and commercial projects.
CuteStockFootage.com Free Videos - over 3,000 various video materials (video transitions, light leaks, particles, green screen videos, video backgrounds, etc.) - licensed under Attribution 4.0 International (CC BY 4.0)
Mazwai Stock Video Creative Commons Stock Video Footage CC licensed (BY-3.0) Free to use, for commercial and non-commercial works, but you must credit the author of the clip.
Free Stock Video Free Stock Video Footage 4k & FULLHD Free to use, for commercial and non-commercial works.
YouTube has a search filter for the CCBY license. However, you need to check if the uploader has indeed the rights to license the audio and video under that license. In some cases, you may need to uncheck "audio" when uploading to Commons using video2commons so only the CCBY-licensed video is uploaded.