I like me some wildlife shows and one of the joys of HD TV has been the gradual move to shooting wildlife documentaries in a format that truly does the subject justice.
Now there is a great free source of videos (and podcasts) that cover a huge variety of subjects. Earth-Touch.com releases videos daily and has a range of podcasts as well, all in stunning HD. They cover a vast array of creatures. For me the Marine HD podcast is especially appealing.
Well done internets.