Microsoft’s PopFly mashup tool is mentioned in chapters 1 and 2 of this book, but as it turns out this product is no longer going to be available come late August.
Unfortunately, on August 24, 2009 the Popfly service will be discontinued and all sites, references, and resources will be taken down. At that time, your access to your Popfly account, including any games and mashups that you have created, will be discontinued. However, Microsoft is still very much dedicated to helping you express your creativity and pursuing a path to software development and offers multiple products to help along the way. If you’re interested in refining your skills in Web applications, please visit Microsoft Web Platform Installer. For those interested in programming on the Xbox, then please visit Microsoft XNA or Microsoft Kodu. And for those who are interested in Windows programming, please visit Microsoft Express. If you have questions or concerns or just want to drop us a line, contact us at email@example.com.
You can find more in this announcement from Microsoft.