Goodreads - See what your friends are reading.

bookish - Help readers discover their next favorite book

LibraryThing - A home for your books.

ReadUpNext - Explore and find your next good read - recommended books by influential people, handpicked by genre or curated for specific interests.

Bookology - Monitor progress by page or percentage, organize collections, use a reading timer with session logs, jot notes, rate finished books, analyze daily activity on a visual calendar, sync across devices, and access advanced stats through Pro for reading …

aNobii - aNobii is a social network for listing books, sharing insights, and meeting people.