SoundCloud allows you to record audio with amazing ease. Using this app you can record sound snippets from students or yourself to place on a website or presentation. Imagine instead of just uploading a image of student work to your classroom webpage, you could also have a link to a audio clip of a student describing what they did or something interesting they learned.
This could also be helpful in helping students that have a fear of public presentations or speech issues. Students could record their speech in private only to be listened to later by the rest of the classroom. There are many great possibilities for this gem of a free app.
Bonus: Check out my blog, The Web, to see how SoundCloud can be used on a regular laptop or computer.