Sortd - Rated the #1 App for Gmail
Goodreads - See what your friends are reading.
KanbanMail - A Kanban board for your emails.
GoodBooks.io - Largest curated collection of 8,500+ book recommendations.
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Bookicious - Find the best new book to read with books collections for makers, founders and entrepreneurs.