Sounds has long been forgotten as part of a good user interface (UI). We have all learned to turn our computer speakers off when browsing the web out of fear of some obnoxious noise from a website. This has made a lot of web user interface experts forget sound as a great UI tool. Sounds are an incredible way to provide quick user feedback. We recently had a series of user stories (see Agile software development if you don't know what a user story is) that said things like "As a user on the scan package page I should hear a Positive Beep." This lead us to wonder what a Positive Beep sounds like. We stumbled across a great site with lots of great sounds for your next mobile application.
Check it out: Lots of great sounds for your mobile application