My DH is as big a fan as I am! I have seasons 1&2 on DVD (and I very, very seldom purchase any movies) and have watched them again. I've also loaned out to friends who missed it and they are now hooked. We are enjoying season 3. PBS will have each episode available to watch online the week following its broadcast -- go to the pbs.org website. Also, if you have Netflix, you can catch Season 1 right now as well if you missed it or want to see it again.
My daughter is part of an online craft group and she coordinated a Downton swap last year. Everyone came up with some fun items for their swap that fit the Downton theme.