Gumlet is a wonderful little tool that I use for optimising your images and thus your website loading speeds. We use it for our work (and client projects) and it works very well!
Pros: - Inbuilt CDN - Easy integration with Wordpress - on-the-fly image manipulation is awesome - Supports CNAME now!
Cons: - Missing some smart (AI-like) image manipulation features that Cloudinary has like Smart/Face-cropping for example. Would love to have those!