Imgur - Imgur is a free and simple image hosting service with image editing feature. Signup is optional.
Flickr - image and video hosting website
Picorator - Picorator is a simple yet powerful image sharing application developed by online communities.
Photobucket - Photobucket offers image hosting and free photo and video sharing.
imgbox - Imgbox is a free image hosting service.
ImgBB - Upload and share your images.