del.icio.us has fast become part of the heartbeat of the Web, giving millions of Web users, both casual and hardcore, an online social network in which to collect, organize, and share their favorite web resources. Using a "hidden" underlayer of tools offered by del.icio.us, you now have the potential to tap into this social network and its rich data in order to expand your own website and applications to a whole new array of possibilities. This book will help you make the most of these possibilities by mixing your data and applications with other web services, and using your own innovative ideas to create something useful, unique, and perhaps even fun. Expert developer Brett O'Connor skillfully guides you deep inside the del.icio.us API, and presents you with a variety of mashup fundamentals such as REST, XML, and Ajax. He shows you how to find and use the best technologies and techniques so that you can create your own robust mashups and remixes with the del.icio.us API and its data. Integrated through the pages you will find real-world examples that demonstrate how to apply this information when building your own cutting-edge website. With this book, you'll discover: * Tips on how to uncover and use mashup tools * How to mash del.icio.us and WordPress * Steps for remxing del.icio.us with Greasemonkey * Methods for collecting references with a custom Firefox(r) plug-in * Techniques to aggregate, organize, and display your research in a custom del.icio.us-powered project hub * How to remix real-time del.icio.us data into image slideshows and streaming music playlists * Techniques to minimize your API calls in order to improve performance and be a respectful mashup developer