HackerRank - HackerRank is a platform that allows companies to conduct interviews remotely to hire developers and for technical assessment purposes.
Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
AlgoExpert.io - A better way to prep for tech interviews
Standard Notes - A safe place for your notes, thoughts, and life's work
Codility - Codility provides a SaaS platform with advanced validation, security and protection features to evaluate the skills of software engineers.
Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.