I use WordPress which pings a lot of services. However, I don't know which one it is that gets my site in Google within minutes. I want to just ping that service, because I'm having problems with people stealing feeds from our sites. Hopefully, that will cut it down and I can put some type of notice in the feed stating that the feed is for use on Google's site only.
If you're using WordPress as a blogging platform, this will help. However, I do not advise using this if you use WordPress as a content management system. http://www.google.com/help/blogsearch/pinging_API.html
Because the pinging service is for bloggers only - if you use it to ping Google every time a regular page is updated when using WordPress as a regular CMS (like Joomla or Drupal) instead of a blog, you might be in for a world of hurt. Check Google's Terms of Service (or email them) to find out for certain beforehand though.