Update for 2008:
Several ping services have disabled (or moved) their ping url’s. Pingomatic has been growing, and they now ping more sites.
From reading their blog, it looks like they keep up well with technical changes required by the sites they ping.
Additionally, some services that have disabled their ping url’s now only seem to accept pings coming from pingomatic directly.
I deemed it therefore better from now on to use pingomatic with an additional list of ping services not supported by pingomatic.
Here’s the updated list (just copy and paste this list into Options > Writing > Update Services):
http://rpc.pingomatic.com
www.blogpeople.net/servlet/weblogUpdates
When I noticed all the ping lists available for WordPress I decided to make a clean list from all the sources, available at:
http://www.warriorforum.com/forum/topic.asp?TOPIC_ID=57413
blogsearch.google.com/ping/RPC2
mod-pubsub.org/kn_apps/blogchatt
rpc.tailrank.com/feedburner/RPC2
trackback.bakeinu.jp/bakeping.php
www.blogpeople.net/servlet/weblogUpdates
www.blogstreet.com/xrbin/xmlrpc.cgi
Any Changes let me know, Thanks!

