Readwise - Effortlessly rediscover and organize your Kindle highlights
Scrapbox - A new style of note-taking that lets you create, discuss, and learn together in one self-organizing space.
Clippings.io - Organize the notes you make on your Kindle
Idea Notebook - Idea Notebook is an app that allows you to keep track of your logs business ideas and track as well as organize them.
Klib - Kindle & iBooks Highlights Manager
NoteKit - A GTK3 hierarchical markdown notetaking application with tablet support.