There are two places you can download the code for the examples in the book. First, you can download it from mashupguide.net:
http://examples.mashupguide.net/ProWeb20MashupsCode.zip
Alternatively, you can go to Apress. That is,
http://apress.com/book/downloadfile/3901
specifically,
http://apress.com/resource/bookfile/3901
(Beware that the mime-type of the page is not set correctly for the web server. You may need to right click on the link and choose "Save File As" or "Download Linked File As")