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?