Interactivity (commenting on images)

What I'd like to be able to do is figure out a way that students can comment throughout my course on, for example, some of the images that I use. In a blog, students can add comments to posts or images that are included in the blog. In Flickr (or other online photo sites), users can always add comments to images. Now, I've just got regular html pages, and the question is how can I make them more interactive for users. I'd like to see students build up a line of commentary on specific images that I use.