Here is are sound mapping projects you might like.

Soundtrack shows you where the sound is happening and where the person recording the sound is moving.

thefreesoundproject are mostly short samples and ambient audio that have been geotagged onto google earth.

There is a website called Soundtransit and I decided to visit Mexico City and hear the sounds. Very nice. You can go anywhere.

If you want to add interesting moods to layer into your sound recordings, you can get free mp3s of atmospheres here at Future Wave Shaper, and many other sites.