Just like YouTube, there is a way to filter search results by license. Unlike YouTube, you can find videos based on specific licenses under Creative Commons (CC BY, CC BY-NC, CC BY-NC-SA, etc.).
Posts in Category
Although the standard license in YouTube is not Creative Commons, contributors can elect to publish their videos as CC BY. Once you search for a video, you can filter the results by license and get a list of all the Creative Commons videos.
A wonderful collection of Creative Commons stock footage. Searchable by keyword and by category.
A great collection (from Archive.org) of stock footage. Licenses vary, and most of these clips are not meant as standalone assets – they are designed to be incorporated into bigger projects.
Free stock video! The licenses are very flexible (many CC BY), and new content is added every week.