Here's an interesting O'Reilly book:
Real World Web Services
ISBN: 0-596-00642-X, 222 pages, $29.95 US, $43.95 CA
"The core idea behind "Real World Web Services" is simple: after years of
hype, what are the major players really doing with web services? Standard
bodies may wrangle and platform vendors may preach, but at the end of the
day what are the technologies that are actually in use, and how can
developers incorporate them into their own applications? Those are the
answers this book delivers."
"The heart of the book is a series of projects, demonstrating the use and
integration of Google, Amazon, eBay, PayPal, FedEx, and many more web
services. Some of these vendors have been extremely successful with their
web service deployments. For example, eBay processes over a billion web
service requests a month."
"Iverson focuses on building 8 fully worked-out example web applications
that incorporate the best web services available today. The book
thoroughly documents how to add functionality like automating listings for
auctions, dynamically calculating shipping fees, automatically sending
faxes to your suppliers, using an aggregator to pull data from multiple
news and web service feeds into a single format or monitoring the latest
weblog discussions and Google searches to keep web site visitors on top of
topics of interest by integrating APIs from popular web sites."
"Real World Web Services" doesn't engage in an intellectual debate as to
the correctness of web services on a theological level. Instead, it
focuses on the practical, real world usage of web services as the latest
evolution in distributed computing, allowing for structured communication
via internet protocols. As you'll see, this includes everything from
sending HTTP GET commands to retrieving an XML document through the use of
SOAP and various vendor SDKs."