digiKam - Professional Photo Management with the Power of Open Source
ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
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.
Batch Image Resizer - Resize, crop, shrink, flip, exif-rotate, convert, enhance, process multiple pictures and photos with professional software! 120+ Actions, 30+ Image Formats
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
Ralpha Image Resizer - High-speed image batch conversion tool