TubeLister - Generate a YouTube playlist from your opened tabs.
OrganizeTube - Create video playlists from Youtube, Vimeo and other sources
Learnamic - Free and paid K-12 learning resources from hundreds of providers, including educational apps, YouTube videos, online classes, printable worksheets, and more.
Vidlis - Create music playlists from YouTube videos.
Playmoss - Create playlists from YouTube, Vimeo and SoundCloud
SoundSlice - The best way to learn music from your heroes