WordPress Update Services are tools which are used to let other people know you’ve updated your blog.
WordPress automatically updates popular Update Services when you have updated your blog by sending pings each time you create or update a post.
Listed below are Ping Services WordPress uses:
http://rpc.pingomatic.com http://rpc.twingly.com http://api.feedster.com/ping http://api.moreover.com/RPC2 http://api.moreover.com/ping http://www.blogdigger.com/RPC2 http://www.blogshares.com/rpc.php http://www.blogsnow.com/ping http://www.blogstreet.com/xrbin/xmlrpc.cgi http://bulkfeeds.net/rpc http://www.newsisfree.com/xmlrpctest.php http://ping.blo.gs/ http://ping.feedburner.com http://ping.syndic8.com/xmlrpc.php http://ping.weblogalot.com/rpc.php http://rpc.blogrolling.com/pinger/ http://rpc.technorati.com/rpc/ping http://rpc.weblogs.com/RPC2 http://www.feedsubmitter.com http://blo.gs/ping.php http://www.pingerati.net http://www.pingmyblog.com http://geourl.org/ping http://ipings.com http://www.weblogalot.com/ping
Update service URL’s are listed under “Update Services” under Settings-> Writing Settings