Recently, while browsing, I came across Autopinger, a free blog cum podcast ping tool that completely automates the pinging tasks for you. Apart from this, AutoPinger also gives more descripting status of the ping request, and you can add any number of blogs to Autopinger and they will automatically ping them for you at 30 minutes interval. That takes all the blog pinging worries out of your mind.

More info: AutoPinger.com | Official Autopinger Blog | Health of Blog Ping Services