FreeSound.org is a website from where you can get audio files that are released under Creative Commons licenses. That means you can use them free of charge with various usage restrictions. There are public domain sounds, which you can use without doing anything. There are sounds that you can do anything with as long as you give the author credit. And there are sounds that you can use for anything except commercial purposes. The FreeSound database is vast and has great searching and browsing capabilities. You can find almost any sound you need on this website.

Audacity is a free open source audio editor for recording, slicing, and mixing audio that runs on many different operating systems. Audacity works great for converting between multiple file types, which is great for us since we need to support different audio types for different browsers. It supports all of the main audio types used by the major web browsers, including Ogg, MP3 and WAV.