I just added a blog to my site of 15 years and put up my first post several days ago. I'm not using a CMS -- this is hand-coded.
I placed the blog in a new subdirectory (root/blog/) and set up an rrs.xml page (for feeds) under that directory. After posting, I manually submitted to Pingomatic. Then I added my blog to my feed reader account, and the post showed up.
I also set up a Google alert for an exact-phrase match from my post to see if/when Google's blog-indexer would list it and alert me. However, I've received no alerts yet, and my post has not been indexed (at least not by Google).
So I'm wondering: Do G and the other blog indexers wait for at least a certain number of posts from a new blog before indexing? Or is there some other explanation?
Is this blog referenced in your sitemap? Do you have links to the blog from indexed pages on your site? If you use Google Webmaster Tools you can request a test of the URL to see if it can be crawled without any problem.