Annotate.tv - Optimize your learning on YouTube
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Slid - Capture knowledge from online videos, courses, and webinars
Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.
Simply.Digital - Goals & Tasks - Todo list to track your time & help set meaningful deadlines
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.