What books are must buy for learning Web Services?

I know some sites are using web services such as yahoo. I would like to
understand how to work with data feeds using web services to presented on different mediums (browser, pda or another application) and how to make it interactive based on the data feed?

Without a doubt, the book by Steve Graham, Building Web Services with Java: Making Sense of XML, SOAP, WSDL and UDDI. It is a couple of years old, but I am as happy with it today as I was when I first bought it. I heard Steve speak on a Webcast by IBM and was so impressed that I immediately ordered his book. When I last contacted Steve, he said a second edition was in the works but did not mention a date. Check the following link from Amazon.com:
http://www.amazon.com/exec/obidos/tg/detail/-/0672321815/
Regards,

Jean,
Are you sure you are looking for Web Services, I would suggest you start with some text on RSS (Really Simple Syndication).
I haven't seen any books on RSS...hmmm, but the RSS specification is available at http://blogs.law.harvard.edu/tech/rss and a lot of sites publish content with it (http://news.com.com/2009-1090_3-980549.html?tag=ne.ft.si.rss). Most blogs and portals use a version of RSS for content (Slashdot among them) without the a Web Services infrastructure! This content can easily be moved to different device footprints.
Once you have your basics in RSS, step back and decide where you want to go and maybe Web Services will fit better into your idea.
Just a few thoughts :-)

thanks for book recommendation and possible solution to my problem.

What about J2EE webservices by Richard Monsfel?

beginning java web services by Bequet, Kunnumpurath, Rhody, Tost
Wrox, ISBN 1-86100-753-1

Originally posted by Pradeep Bhat:
What about J2EE webservices by Richard Monsfel?

I believe Kyle Brown has a copy. I know he's a busy man but maybe we could bribe him into writing a review...