If it's the Board of Supes you're looking to subscribe to, you've got to navigate through "Video on Demand" (even if you're seeking audio, not video), then click "Board of Supervisors," and then pick the committee to which you want to subscribe, then scroll waaaaaay down to the bottom to find podcast links such as this one for the regular Board of Supes meetings, or this one for the Rules Committee. There's about 40 or so different podcasts being offered. DUDE, SCORE!
So, now, you may be wondering: is there a list of all the available podcasts, so I can browse them and choose the ones I want? Not exactly. You'll need to browse the long lists of committees on the SF Gov TV website, opening each one's page one at a time, to find the subscription links. Because there's nothing that users love more than clicking on links to more links, and waiting for pages to load so that they can be presented with even MORE links to links.
Good news, though: we spoke to SF Gov TV today, and they told us that they're going to be available on iTunes soon, so their subscriptions will be easy to find. Instead of, you know, hard. Just don't try to subscribe to the City & Local School District Committee. They've got an ampersand in the title, and that totally screws up the XML. Whoops! Nice to see the city practices rigorous bug-testing.