Third party cache appliances are configured into a content delivery service to enable such devices to cache and serve content that has been tagged for delivery by the service. The invention enables the content delivery service to extend the reach of its network while taking advantage of high performance, off-the-shelf cache appliances. If the third party caches comprise part of a third party content delivery network, the interconnection of caches to the CDS according to the present invention enables the CDS and the third party network to share responsibility for delivering the content. To facilitate such "content peering," the CDS may also include a traffic analysis mechanism to provide the third party network with preferably real-time data identifying the content delivered by the CDS from the third party caches. The CDS may also include a logging mechanism to generate appropriate billing and reporting of the third party content that is delivered from the cache appliances that have been joined into the CDS.