digiKam - Professional Photo Management with the Power of Open Source
Darktable - darktable is an open source photography workflow application and raw developer.
JetPhoto Studio - JetPhoto Studio is a sleek and easy-to-use digital photo software that allows users to manage their photos in an attractive, intuitive mode and turning a sometimes frustrating chore into a fun and easy way by clicking only several steps.
RawTherapee - RawTherapee is a free RAW converter and digital photo processing software.
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
DVDVideoSoft Image Convert and Resize - Free Image Convert and Resize is a compact yet powerful program for batch mode image processing.