Here is a list I compiled from http://codex.wordpress.org/Update_Services and http://www.blogspottutorial.com/2009/01/xml-rpc-ping-service-list.html.
An XML-RPC list is a list of “pinging” services that allow you to notify other blogs and blogging services of your updates. Most blogging software will allow you the option to add in your own URLs to “ping” once you’ve made updates to the site.
For example, in WordPress, you can go to General>Writing>“Update Services” and add in your own.
UPDATE! 10/13/10
I’ve recently found some cool plugins that help you auto-ping and help keep your pings from becoming nuisances and thus getting you banned/blacklisted. Check out the list here:
http://www.internetgeeks.org/blog/how-to-use-wordpress-ping-utility-without-getting-banned/
Download the list
For this list, the duplicates have been removed and made into excel spreadsheet format for quick copy/paste/editing. Enjoy!