Google announced the Google Blog Search Pinging Service today. If you want to make sure your latest posts appear in Google's Blog Search then, like other services including Technorati or Weblogs.com, you will want to ping them when you update. This can be done in two ways:

Manual Ping

If you're not technically minded and want the simplest method of pinging Google, simply go to http://blogsearch.google.com/ping and enter your blog's URL everytime it updates.

Automatic Ping

If you want to let Wordpress deal with your pings for you everytime you update then do the following: in your Wordpress admin area, go to "options" then "writing". At the bottom of the page you should find the Update Services section. By default this should have rpc.pingomatic.com in the text box. This is fine, as Pingomatic pings a number of services for you. It doesn't cover Google Blog Search directly though. To add this you need to add http://blogsearch.google.com/ping/RPC2 to the Update Services box, on a new line.

That's it, now you can keep Google, as well as all the other update services, interested when you post. For a more comprehensive list of update services, please see this all inclusive ping list.