I am interested in seeing what people are doing with the free sound API in terms of manipulating sound. It is a comprehensive and easily searchable database of found sound.
There is their project with mapping the geo-tagged sounds in their database. I particularly enjoy zooming way in on sounds that occur inside of an inclosed space.
I mentioned this project earlier, but it is also appropriate here. Ali Momeni did a project where you explored different sounds in the database through the exaggerated movements of a stylus.