I use Twitterfeed.com to send my blog posts to Twitter automatically. There are also Facebook applications and Linked In options to import your updates from Twitter. So, the sequence looks like this...

1) Record a podcast

2) Upload the podcast to my blog, and write a blog post for show notes

3) Twitterfeed issues a "tweet" to my Twitter followers with a link to my blog (via bit.ly so the URL is short, leaving room for the blog post headline

4) The tweet gets posted to my Facebook feed where all my Facebook friends see it (NOTE: Twitter feeds have a few strange things in them that some Facebook users may not recognize or understand, like @, RT # codes and the bit.ly URLs)

5) The tweet also goes to my Linked In status feed, with the same potential issues as with Facebook regarding cryptic codes.

There are probably other ways to spread the word even further automatically. Once this is set up, it works well.