From the Overclockers Australia forum comes an interesting project to watch - the "HydraSonic - Arduino Controlled Whole House Matrix Audio System". Member "davros123" is in the process of creating what will be a fascinating Arduino and web-controlled audio system for multiple zones and rooms with levels of intelligence only seen in commercial systems costing ten times as much. Although the project is a work-in-progress, we look forward to reading more about it and following the design journey.
It's complex projects like the one above that show how an Arduino system can work with other platforms and technologies to create worthwhile projects. If this type of system is of interest, you will enjoy the book "Practical Arduino" by Jonathan Oxer and Hugh Blemings:
Using this book you can create your own Arduino-based designs, gain an in-depth knowledge of the architecture of Arduino, and learn the easy-to-use Arduino language all in the context of practical projects that you can build yourself at home. Get hands-on experience using a variety of projects and recipes for everything from home automation to test equipment. For more information and to order, click here.