Scida

Scida is an e-book library management app for Mac that helps you organize your e-book collections and manage your Kindle.

Books cannot only be copied between your computer and Kindle but Scida also provides usage statistics about your Kindle, and you can edit your Kindle's collections for certain devices (Kindle Keyboard, Kindle 4 and Kindle black).
Features: You can import your e-books and e-book folders to your Scida library Collections can be created within Scida library to organize your e-books Scida auto-detects if your Kindle is connected and you can browse its content You can import books from your Kindle to your local library You can send books from your local library to your Kindle Usage information is available about your Kindle If you have a Kindle Keyboard, Kindle 4 and Kindle black, you can create, edit and delete your Kindle's collections and add or remove books
Supported devices: Kindle Keyboard (Kindle 3), Kindle 4, Kindle Touch, Kindle black (2012), Kindle Paperwhite (Scida does not support Kindle DX, Kindle Fire tablets, first and second generation Kindles.)
Supported e-book formats: .mobi .prc .azw