The beauty of WordPress is that it automatically tells Google (and a bunch of other sites) to look at your post- every time you post. But, there are a lot of other ping services as you can see in this post:

SEOposition.com Blog » List of Pinging Services for your Blog

Ping services simply let other sites know when your site has updated. By allowing XML-RPC or (pings) as they are more commonly called, sites will know almost instantaneously when you update new blog posts or content. In turn, they will update their indices accordingly.These notifications, or pings, are valuable in many ways although I think you can also “over submit” if you’re not careful. It really depends if the site’s using the ping have URLs that are indexed in search engines. Most are dynamic search pages only, so they are fine.

Here’s a list of pinging services you can use with your blog…
http://rpc.pingomatic.com/
http://api.feedster.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://ping.bitacoras.com
http://ping.blo.gs/
http://ping.bloggers.jp/rpc/
http://ping.cocolog-nifty.com/xmlrpc
http://ping.feedburner.com
http://ping.rootblog.com/rpc.php
http://ping.syndic8.com/xmlrpc.php
http://ping.weblogs.se/
http://rcs.datashed.net/RPC2
http://rcs.datashed.net/RPC2 euro.weblogs.com
http://rpc.blogrolling.com/pinger/
http://rpc.technorati.com/rpc/ping
http://rpc.weblogs.com/RPC2
http://thingamablog.sourceforge.net/ping.php
http://topicexchange.com/RPC2
http://www.a2b.cc/setloc/bp.a2b
http://www.bitacoles.net/ping.php
http://www.blogdigger.com/RPC2
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.catapings.com/ping.php
http://www.lasermemory.com/lsrpc/
http://www.mod-pubsub.org/kn_apps/blogchatter/ping.php
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/