Ladies and gentlemen, I present to you the definitive list of XML RPC ping services.
Blogs should publicize new posts by letting blog search engines and feed aggregators know about changes. Update Services are tools used to let other people know you've updated your blog.
I went through every ping service list in the top 100 relevant Google search results. I compiled a master list of over 3,000 ping services from roughly 40 sites and then simply removed the duplicates using a quick script. After that I removed the approximately 80 duplicate and misspelled URLs (by hand), leaving exactly 250 URLs.
For your pinging pleasure, the refined list of XML RPC ping services:
http://1470.net/api/ping
http://a2b.cc/setloc/bp.a2b
http://api.feedster.com/ping
http://api.feedster.com/ping.php
http://api.moreover.com/ping
http://api.moreover.com/RPC2
http://api.mw.net.tw/RPC2
http://api.my.yahoo.com.jp/RPC2
http://api.my.yahoo.com/ping
http://api.my.yahoo.com/rpc2
http://api.my.yahoo.com/rss/ping
http://audiorpc.weblogs.com/RPC2
http://bblog.com/ping.php
http://bitacoles.net/notificacio.php
http://bitacoles.net/ping.php
http://bitacoras.net/ping/
http://blo.gs/ping.php
http://blog.goo.ne.jp/XMLRPC
http://blog.goo.ne.jp/XMLRPCishinao.net
http://blog.with2.net/ping.php
http://blog.youdao.com/ping/RPC2
http://blogbot.dk/io/xml-rpc.php
http://blogdb.jp/xmlrpc/
http://blogdigger.com/RPC2
http://blogmatcher.com/u.php
http://blogoole.com/ping/
http://blogoon.net/ping/
http://blogpeople.net/ping
http://blogpeople.net/servlet/weblogUpdates
http://blogping.unidatum.com/RPC2/
http://blogsdominicanos.com/ping
http://blogsearch.google.ae/ping/RPC2
http://blogsearch.google.at/ping/RPC2
http://blogsearch.google.be/ping/RPC2
http://blogsearch.google.bg/ping/RPC2
http://blogsearch.google.ca/ping/RPC2
http://blogsearch.google.ch/ping/RPC2
http://blogsearch.google.cl/ping/RPC2
http://blogsearch.google.co.cr/ping/RPC2
http://blogsearch.google.co.hu/ping/RPC2
http://blogsearch.google.co.id/ping/RPC2
http://blogsearch.google.co.il/ping/RPC2
http://blogsearch.google.co.in/ping/RPC2
http://blogsearch.google.co.it/ping/RPC2
http://blogsearch.google.co.jp/ping/RPC2
http://blogsearch.google.co.ma/ping/RPC2
http://blogsearch.google.co.nz/ping/RPC2
http://blogsearch.google.co.th/ping/RPC2
http://blogsearch.google.co.uk/ping/RPC2
http://blogsearch.google.co.uk/pingRPC2
http://blogsearch.google.co.ve/ping/RPC2
http://blogsearch.google.co.za/ping/RPC2
http://blogsearch.google.com.ar/ping/RPC2
http://blogsearch.google.com.au/ping/RPC2
http://blogsearch.google.com.br/ping/RPC2
http://blogsearch.google.com.co/ping/RPC2
http://blogsearch.google.com.do/ping/RPC2
http://blogsearch.google.com.mx/ping/RPC2
http://blogsearch.google.com.my/ping/RPC2
http://blogsearch.google.com.pe/ping/RPC2
http://blogsearch.google.com.sa/ping/RPC2
http://blogsearch.google.com.sg/ping/RPC2
http://blogsearch.google.com.tr/ping/RPC2
http://blogsearch.google.com.tw/ping/RPC2
http://blogsearch.google.com.ua/ping/RPC2
http://blogsearch.google.com.uy/ping/RPC2
http://blogsearch.google.com.vn/ping/RPC2
http://blogsearch.google.com/ping/RPC2
http://blogsearch.google.com/ping/RPC2
http://blogsearch.google.de/ping/RPC2
http://blogsearch.google.es/ping/RPC2
http://blogsearch.google.fi/ping/RPC2
http://blogsearch.google.fr/ping/RPC2
http://blogsearch.google.gr/ping/RPC2
http://blogsearch.google.hr/ping/RPC2
http://blogsearch.google.ie/ping/RPC2
http://blogsearch.google.in/ping/RPC2
http://blogsearch.google.it/ping/RPC2
http://blogsearch.google.jp/ping/RPC2
http://blogsearch.google.lt/ping/RPC2
http://blogsearch.google.nl/ping/RPC2
http://blogsearch.google.pl/ping/RPC2
http://blogsearch.google.pt/ping/RPC2
http://blogsearch.google.ro/ping/RPC2
http://blogsearch.google.ru/ping/RPC2
http://blogsearch.google.se/ping/RPC2
http://blogsearch.google.sk/ping/RPC2
http://blogsearch.google.tw/ping/RPC2
http://blogsearch.google.us/ping/RPC2
http://blogsearch.google.us/pingRPC2
http://blogshares.com/rpc.php
http://blogsnow.com/ping
http://blogstreet.com/xrbin/xmlrpc.cgi
http://blogupdate.org/ping/
http://blogupdate.org/sverige/ping/
http://bulkfeeds.net/rpc
http://catapings.com/ping.php
http://coreblog.org/ping/
http://cullect.com/feed/ping
http://effbot.org/rpc/ping.cgi
http://feedsky.com/api/RPC2
http://fgiasson.com/pings/ping.php
http://focuslook.com/ping.php
http://geourl.org/ping
http://godesigngroup.com/blog/feed/
http://hamo-search.com/ping.php
http://holycowdude.com/rpc/ping/
http://imblogs.net/ping/
http://j-ranking.com/ping.cgi
http://lasermemory.com/lsrpc/
http://mod-pubsub.org
http://mod-pubsub.org/kn_apps/blogchatter/ping.php
http://mod-pubsub.org/ping.php
http://newsblog.jungleboots.org/ping.php
http://newsisfree.com/rpccloud
http://newsisfree.com/xmlrpctest.php
http://packetmonster.net/xmlrpc.php
http://ping.amagle.com/
http://ping.bitacoras.com/
http://ping.blo.gs/
http://ping.blogg.de/
http://ping.bloggers.jp/rpc/
http://ping.blogmura.jp/rpc/
http://ping.blogoon.net/
http://ping.blogs.yandex.ru/RPC2
http://ping.cocolog-nifty.com/xmlrpc
http://ping.exblog.jp/xmlrpc
http://ping.fakapster.com/rpc
http://ping.fc2.com/
http://ping.feedburner.com/
http://ping.feeds.yahoo.com/RPC2/
http://ping.gpost.info/xmlrpc
http://ping.kutsulog.net/
http://ping.myblog.jp/
http://ping.namaan.net/rpc
http://ping.pubsub.com/ping/
http://ping.rootblog.com/rpc.php
http://ping.sg/rpc/alfanhendro/adsense
http://ping.snap.com/ping/RPC2
http://ping.speenee.com/xmlrpc
http://ping.syndic8.com/xmlrpc.php
http://ping.weblogalot.com/rpc.php
http://ping.weblogs.se/
http://ping.wordblog.de/
http://pinger.blogflux.com/rpc/
http://pinger.onejavastreet.com
http://pingoat.com/
http://pingoat.com/goat/rpc2
http://pingqueue.com/rpc
http://pingqueue.com/rpc/
http://r.hatena.ne.jp/rpc
http://rcs.datashed.net
http://rcs.datashed.net/rpc2
http://rcs.datashed.net/RPC2
http://rcs.datashed.net/RPC2/
http://rpc.blogbuzzmachine.com/rpc2
http://rpc.blogbuzzmachine.com/RPC2
http://rpc.blogcatalog.com
http://rpc.blogcatalog.com/
http://rpc.bloggerei.de/ping
http://rpc.bloggerei.de/ping/
http://rpc.blogrolling.com/pinger
http://rpc.blogrolling.com/pinger/
http://rpc.britblog.com
http://rpc.britblog.com/
http://rpc.feedsky.com/ping
http://rpc.icerocket.com:10080
http://rpc.icerocket.com:10080/
http://rpc.icerocket.com:10080/
http://rpc.newsgator.com
http://rpc.newsgator.com/
http://rpc.pingomatic.com
http://rpc.reader.livedoor.com/ping
http://rpc.shareapost.com/
http://rpc.tailrank.com/feedburner/RPC2
http://rpc.technorati.com/rpc/ping
http://rpc.technorati.jp/rpc/ping
http://rpc.twingly.com
http://rpc.twingly.com/
http://rpc.weblogs.com/RPC2
http://rpc.wpkeys.com
http://rpc.wpkeys.com/
http://rssfeeds.com/suggest_wizzard.php
http://rssfwd.com/xmlrpc/api
http://serenebach.net/rep.cgi
http://services.newsgator.com/ngws/xmlrpcping.aspx
http://signup.alerts.msn.com/alerts-PREP/submitPingExtended.doz
http://snipsnap.org/RPC2
http://syndic8.com/xmlrpc.php
http://thingamablog.sourceforge.net/ping.php
http://topicexchange.com/RPC2
http://trackback.bakeinu.jp/bakeping.php
http://wasalive.com/ping
http://wasalive.com/ping/
http://weblogalot.com/ping
http://weblogues.com/ping/
http://weblogues.com/rpc
http://weblogues.com/RPC
http://weblogues.com/RPC/
http://www.a2b.cc/setloc/bp.a2b
http://www.bitacoles.net/ping.php
http://www.blogdigger.com/RPC2
http://www.bloglines.com/ping
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.blogroots.com/tbpopuli.blog?id=1
http://www.blogsdominicanos.com/ping/
http://www.blogshares.com/rpc.php
http://www.blogsnow.com/ping
http://www.blogstreet.com/xrbin/xmlrpc.cgi
http://www.blogupdate.org/ping/
http://www.catapings.com/ping.php
http://www.feedsky.com/api/RPC2
http://www.focuslook.com/ping.php
http://www.holycowdude.com/rpc/ping/
http://www.i-learn.jp/ping/
http://www.imblogs.net/ping/
http://www.kping.com/
http://www.lasermemory.com/lsrpc/
http://www.mod-pubsub.org/kn_apps/blogchatter/ping.php
http://www.mod-pubsub.org/knapps/blogchatter/ping.php
http://www.mod-pubsub.org/ping.php
http://www.newsisfree.com
http://www.newsisfree.com/RPC
http://www.newsisfree.com/RPCCloud
http://www.newsisfree.com/xmlrpctest.php
http://www.octora.com/add_rss.php
http://www.packetmonster.net/xmlrpc.php
http://www.rssfwd.com/xmlrpc/api
http://www.snipsnap.org/RPC2
http://www.syndic8.com/xmlrpc.php
http://www.twingly.com/ping
http://www.volny.cz/tile2007/bathroom1tile/bathroom-tile.htm
http://www.wasalive.com/ping/
http://www.weblogalot.com/ping
http://www.weblogues.com/ping/
http://www.weblogues.com/RPC
http://www.xianguo.com/xmlrpc/ping.php
http://www.zhuaxia.com/rpc/server.php
http://xianguo.com/xmlrpc/ping.php
http://xmlrpc.blogg.de
http://xmlrpc.bloggernetz.de/RPC2
http://xping.pubsub.com/ping
http://xping.pubsub.com/ping
http://xping.pubsub.com/ping/
http://xping.pubsub.com/ping/
http://zhuaxia.com/rpc/server.php
http://zing.zingfast.com