http://api.moreover.com/ping
http://api.my.yahoo.com/rss/ping
http://blogsearch.google.com/ping/RPC2
http://ping.bitacoras.com
http://ping.feedburner.com
http://ping.syndic8.com/xmlrpc.php
http://rpc.blogrolling.com/pinger/
http://rpc.icerocket.com:10080/
http://rpc.technorati.com/rpc/ping
http://rpc.weblogs.com/RPC2
http://topicexchange.com/RPC2
http://www.blogdigger.com/RPC2
http://www.blogoole.com/ping/
http://www.popdex.com/addsite.php
http://www.wasalive.com/ping/
http://www.weblogues.com/RPC/
http://blogping.unidatum.com/RPC2/
http://rpc.pingomatic.com/
http://pingoat.com/goat/RPC2/
http://pingqueue.com/rpc/
http://www.bloglines.com/ping

About: when you publish a new post, WordPress automatically notifies the following site update services. Login to your Wordpress open Settings->Writing and then at the bottom of the page under “Update Services” add all the upper ping services.

Status: free, no registration

Blog Ping, Ping Services, Update Services, Wordpress