This presentation: http://talks.php.net/show/webservices-oscon2003]]>

PHP + SOAP + Amazon http://www.onlamp.com/pub/a/php/2003/07/03/php_amazon_soap.html]]>

PEAR::SOAP http://pear.php.net/package-info.php?package=SOAP]]>

Shane Carvaeo's SOAP Presentation http://talks.php.net/show/soap-phpcon-ny2003/]]> (Very detailed.)

Programming PHP]]> - Chapter 11 ("XML") (Mostly XML-RPC.)

PHP Cookbook]]> Recipes:

SOAP: 12.9, 12.10

XML-RPC: 12.7, 12.8

Building & Sending HTTP Requests: 8.9, 11.2

Parsing XML: 12.4, 12.5, 12.6

XML.com's Web services area: http://www.xml.com/webservices/]]>