Pinging is one of those things bloggers take for granted. Ping-o-matic offers a slick service to notify most of the major blog aggregation and search tools that you’ve made a post or updated your site. It offers a smaller subset of directories and resources for podcasters to ping. If you want a purely podcast focused ping tool, AllPodcasts.com seems to be the place to go. For a more comprehensive list of sites you should ping each time you publish a podcast, Research Buzz offers a few additional podcast ping sites and a cool resource for building a ping database in an Excel Spreadsheet (Office 2003 required for this last one, of course). I’d personally rather see a service like Ping-o-matic aggregate this stuff all in one place so I don’t need to maintain my own list. In the meantime, the combination of AllPodcasts.com and the Research Buzz recommendations help guarantee maximum exposure.