digiKam - Professional Photo Management with the Power of Open Source
Call to Idea - A gallery of inspiration for product designers
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
AuthorBee - Organize Twitter around your interests
FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
Voynetch - Share your visual notes and graphic recordings.