Here is a list of Ping Services you can add to your Wordpress blog;  On your dashboard, go to Settings then Writing, scroll down and you will see a box to add this list, copy the list and paste it into this section and click update.

http://blogsearch.google.com/ping/RPC2

http://1470.net/api/ping

http://api.feedster.com/ping

http://api.moreover.com/RPC2

http://api.moreover.com/ping

http://api.my.yahoo.com/RPC2

http://api.my.yahoo.com/rss/ping

http://bblog.com/ping.php

http://bitacoras.net/ping

http://blog.goo.ne.jp/XMLRPC

http://blogdb.jp/xmlrpc

http://blogmatcher.com/u.php

http://bulkfeeds.net/rpc

http://coreblog.org/ping/

http://mod-pubsub.org/kn_apps/blogchatt

http://www.lasermemory.com/lsrpc/

http://ping.amagle.com/

http://ping.bitacoras.com

http://ping.blo.gs/

http://ping.bloggers.jp/rpc/

http://ping.cocolog-nifty.com/xmlrpc

http://ping.blogmura.jp/rpc/

http://ping.exblog.jp/xmlrpc

http://ping.feedburner.com

http://ping.myblog.jp

http://ping.rootblog.com/rpc.php

http://ping.syndic8.com/xmlrpc.php

http://ping.weblogalot.com/rpc.php

http://ping.weblogs.se/

http://pingoat.com/goat/RPC2

http://rcs.datashed.net/RPC2/

http://rpc.blogbuzzmachine.com/RPC2

http://rpc.blogrolling.com/pinger/

http://rpc.icerocket.com:10080/

http://rpc.newsgator.com/

http://rpc.pingomatic.com

http://rpc.technorati.com/rpc/ping

http://rpc.weblogs.com/RPC2

http://topicexchange.com/RPC2

http://trackback.bakeinu.jp/bakeping.php

http://www.a2b.cc/setloc/bp.a2b

http://www.bitacoles.net/ping.php

http://www.blogdigger.com/RPC2

http://www.blogoole.com/ping/

http://www.blogoon.net/ping/

http://www.blogpeople.net/servlet/weblogUpdates

http://www.blogroots.com/tb_populi.blog?id=1

http://www.blogshares.com/rpc.php

http://www.blogsnow.com/ping

http://www.blogstreet.com/xrbin/xmlrpc.cgi

http://www.mod-pubsub.org/kn_apps/blogchatter/ping.php

http://www.newsisfree.com/RPCCloud

http://www.newsisfree.com/xmlrpctest.php

http://www.popdex.com/addsite.php

http://www.snipsnap.org/RPC2

http://www.weblogues.com/RPC/

http://xmlrpc.blogg.de

http://xping.pubsub.com/ping/