Readwise - Effortlessly rediscover and organize your Kindle highlights
Wellput - Export your Kindle highlights into a personalized library
Knotes - An efficient, beautiful Kindle highlights & notes manager
Newsletters to Kindle - Read your newsletters on your Kindle
Clippings.io - Organize the notes you make on your Kindle
Tressel.xyz - Save content from the Internet (like Twitter & Reddit) and export it to Notion, Obsidian & Evernote