Readwise - Effortlessly rediscover and organize your Kindle highlights
Bookicious - Find the best new book to read with books collections for makers, founders and entrepreneurs.
Knotes - An efficient, beautiful Kindle highlights & notes manager
Goodreads - See what your friends are reading.
Clippings.io - Organize the notes you make on your Kindle
Bookcelerator - A curated directory of books that will make you smarter