When a new weblog entry contains an audio enclosure, you can ping Audio.Weblogs.Com, which in turn notifies a lot of services that monitor the site, such as the podcast directory GigaDial.
One gotcha for anyone else working on Audio.Weblogs.Com notification: the site's XML-RPC server is at audiorpc.weblogs.com, not audio.weblogs.com, which I finally discovered when I read the documentation.
Update: Referring to this code as my pinger sounds disturbingly like my twanger.
Reading your update I have a (controllable) urge to hear Chuck Berry's last hit, My Ding-a ling!
My Pod A Ping, My Pod A Ping.
Won't you play with My Pod A Ping!