PhotoDemon - Lightweight portable BSD licensed photo editor for Windows focused on performance and usability.
PicsArt - Explore 100,000,000+ awesome images and photos on the web
PhotoFlare - Quick, simple but powerful Cross Platform image editor.
Camera360 - Let those photos out of their albums and PK with Camera360 users worldwide!
PixBuilder - Free Photo Editing Software for PC
Pixelmator - Pixelmator is an image-editing application for Mac and iPad.