Noisy Typer by Theo Watson is a kick-ass piece of free software which plays amazing typewriter sound effects as you type. The program is simple and just runs in the background. Noisy Typer works with email, web, word and other applications. Sounds effects include, the classic sound of punching down on letter keys, spacebar, backspace, carriage return and scroll up and down. You can download Noisy Typer for free Here (currently for OS X only).