Golden - Mapping all human knowledge
GoodBooks.io - Largest curated collection of 8,500+ book recommendations.
Sutle - Save and organize resources into a directed learning path.
Goodreads - See what your friends are reading.
Postly - Turn your photos into REAL beautiful postcards. Available on iPhone, iPad and Android. Make friends and family smile with a postcard!
LibraryThing - A home for your books.