Silk Slides is a new service for easily sharing and discussing slideshows. It is very easy to use the service. To get started just upload your slides (Keynote files didn't work for me) then enter your email address. When your upload is complete you can share your slides by sending the URL assigned to your slides to anyone you like.
Silk Slides allows commenting on each slide in your slideshow. To post a comment you have to enter your name (or nickname) and an email address.
Applications for Education
Silk Slides could be a good platform for students to use to ask questions about slides that you share with them. You could use Silk Slides to offer feedback to your students about the design and content of their slides too.