SoundCloud is a free online tool for storing and sharing any original audio files you create.  This would be a great tool for students to record themselves reading, then they can share the audio file with the teacher who can then assess their fluency.  Another use could involve students doing the same thing, but in a foreign language course.  A cool feature that SoundCloud has is the ability of the listener to embed comments on the audio file.  Teachers could use this to provide feedback and suggestions to the students' work.  Students could create SoundCloud recordings of themselves to add to a ThingLink (Day 22) interactive image.