We've just added Cloudinary to the add-on catalog. Cloudinary makes working with images in the cloud a breeze and offers a wide array of image manipulation services. They also have a .NET SDK available making it easy for AppHarbor customers to take advantage of their services.
Working with images can be a hassle and we know some of you already use Cloudinary to take the pain out of transforming images. We're excited to offer easy integration with this simple and flexible service and hope you'll find it useful for your applications. Cloudinary has published thorough documentation and samples showing how to use the add-on with AppHarbor - make sure to take a look when you try it out.