Alan talks about creating learning objects with Flickr. I think Flickr is a very interesting platform for education. For example at Lewis, some classrooms will soon be involved in the Flat Stanley Project. Flat Stanley is a book character and a rich tradition has grown up of students creating a paper version of Stanley and then sending him via postal mail to another school for a visit. In the process students at both schools share email (or a weblog post, or now, Flickr posts...) about Stanley's adventures at the visiting school.
Alan Levine talks about the use of "Notes" in Flickr, the photosharing/community web space. Flickr has a feature where a user can assign notes to parts of an image. For example if you had a picture of a group of students, you could assign a note to each student which when moused over would reveal their name. A nice feature for a substitute teacher.