Our web services consumer provides a couple of access methods that can be safely cached:

class Fedora_Object
{
/* .... */
	        public function getDissemination($pid, $sDefPid, $methodName, $parameters, $asOfDateTime = null) {
           try {
                   return Fedora_Repository::get('API-A', $pid)->getDissemination(array('pid' => $pid,
                                                     'serviceDefinitionPid' => $sDefPid,
                                                     'methodName' => $methodName,
                                                     'parameters' => $parameters,
                                                     'asOfDateTime' => $asOfDateTime));
                } catch(SoapFault $s) {
                       return $s;
                }
        }
/* .... */
}

In the bootstrap file, instead of initializing the Fedora_Object class, I wrap it in a Zend_Cache instance:

$fedora = Zend_Cache::factory('Class', 'File', array('cached_entity' => new Fedora_Object(),
                          'cached_methods' => array('getObjectXML', 'getDatastreamDissemination', 'getDissemination'),
                           'cache_by_default' => false));

This code tells Zend_Cache to cache only the specified cached_methods and pass everything else through. Easy.