Readwise - Effortlessly rediscover and organize your Kindle highlights
Universal Book Reader - Just like its name, Universal Book Reader is really a universal book reading application allowing you to read the eBooks from the convenience of your smartphones.
Knotes - An efficient, beautiful Kindle highlights & notes manager
Cool Reader - Fast and small cross-platform eBook reader for desktops and handheld devices
Clippings.io - Organize the notes you make on your Kindle
iReader - iReader is one of the most accomplished ways to read the books right from your smartphones.