Imgur - Imgur is a free and simple image hosting service with image editing feature. Signup is optional.
Flickr - image and video hosting website
imgbox - Imgbox is a free image hosting service.
Photobucket - Photobucket offers image hosting and free photo and video sharing.
PostImage.org - Provides free image upload and hosting integration for forums.
SmugMug - SmugMug is a platform that allows amateurs and professional photographers to host their pictures and create a virtual gallery for promoting and selling their work.