Darktable - darktable is an open source photography workflow application and raw developer.
RawTherapee - RawTherapee is a free RAW converter and digital photo processing software.
DVDVideoSoft Image Convert and Resize - Free Image Convert and Resize is a compact yet powerful program for batch mode image processing.
Affinity Photo - Affinity is the imaging and design suite for creative professionals exclusively for Mac.
OnlineImageResize.com - Free online image resizer. Resize your image fast and easy. Image resizer online!
GIMP - GIMP is a multiplatform photo manipulation tool.