As PyCon draws closer, we're short on volunteers to chair sessions. Session chairs help ensure that the speakers start and stop on time, and assist with the audience during the question-and-answer period. If you're going to be in the same room for an entire block of talks, why not be the chair, too?
For instructions on signing up, see the SessionChairs wiki page. To find an unchaired talk, look at the conference schedule: the pop-up for each talk will display a link to the signup form if no one has volunteered yet.