Bookmark OS - Bookmark OS is like Mac or Windows optimized for bookmarks.
Softorino YouTube Converter - Download YouTube video & audio. Watch and listen offline
Siimpl Bookmarking - Start collecting and organizing what interests you
You-Get - Command-line utility to download media contents from the web
Annotate.tv - Optimize your learning on YouTube
CONV. - Convert YouTube video to MP3, GIF or MP4