I use my ReplayTV to do this. On clearance starting at $350 (including subscription) here: http://www.digitalnetworksna.com/shop/_templates/cat_listRTV.asp?cat=51

Other similar record uses: I also use it to capture rented DVDs that need to be returned before I got to watch them.

Other networked benefits: I move a few hours of recorded TV to my laptop for plane trips.