Slashdot runs a thread on which podcasts people are listening to and why (the crowd is mostly technical, so expect a certain one-sidedness (yup, that’s a real word).
One that I’ve picked up from the comments is Sysadministrivia.com.
If you want more ideas on what to subscribe to, have a look at this blog post I did a while ago. Â It links to a couple of podcast lists.