SOAP::Lite for Perl:

Documentation

Randy J. Ray: Programming Web Services with Perl
An excellent introduction to Web services, and to SOAP, XML-RPC and more. The reference in the back is an indespensible resource.

I just pushed the latest version of SOAP::Lite to CPAN. It is a relatively small release containing the following fixes:

Fixed a bug where the charset parameter was being added and re-added multiple times to the Content-Type HTTP header.
Fixed a bug that prevented SOAP::Lite from parsing MIME messages that did not contain content-ids.
Made a few enhancements to how SOAP::Lite defines (internally) the use of default and non-default namespaces.