Photos and Web 2.0
The social interaction of Web 2.0 services in photo sharing is highly popular and can be an engaging educational tool.
Flickr
Flickr offers users a free space to upload, share, tag, sort, and annotate photos. Groups of pictures also have an RSS feed to which one can subscribe. Recently, there is an added feature of being able to geotag photos. It's an amazing place to visit!

There are endless possibilities for classroom use of Flickr, provided that AUP guidelines and copyright is respected. Below are a few examples:
Explorer Reports 5th grade students at Lewis Elementary School in Portland, Oregon, published their illustrations and reports online at Flickr. (In addition to publishing these on Flickr, their teacher used a tool called MapBuilder to tie those photos into an interactive map.

The K-12 Online Conference has several excellent presentations on how to use Flickr and ideas for classroom use. Getting to Know Flickr by Jeff Utecht is a good introduction on how to use the basic features of Flickr. Alan Levine's presentation, I Did Not Know You Could do THAT with Free Web Tools has one component called What Can We Do With Flickr?, which is an amazing and unique presentation done in Flickr that shows how to use some of the more advanced features.

For more ideas on how to use Flickr in the classroom, read David Jake's blog post called Classroom Uses of Flickr and Uh-oh, Another Flickr Post. The latter involves using photos from Flickr to tell compelling digital stories. A must read!

BubbleShare
Bubbleshare is a Web 2.0 service that allows users to upload pictures, record a narration, add notation, and host a finished digital story on their site while displaying the show on a blog or wiki. What a great tool!
An example of classroom use can be found at the K-12 Online Conference, in a presentation by Kathy Cassidy, Using Web 2.0 Tools in a Grade One Classroom. In her presentation, she demonstrates how BubbleShare is used as a slideshow generator for her classroom blog.