When I was writing my historical fantasy, I watched The Patriot, and also, National Treasure. The Patriot was great for period details, and National Treasure for getting me excited all over again about the Revolutionary War and Benjamin Franklin (who was in my book).
Right now I'm drafting a fantasy with 1920 ties, and so I recently just finished the tv series, Downton Abbey. I kept a notebook to jot down certain phrases to incorporate into my book, as well as a sharp eye on the outfits that were being worn. I also want to rewatch The Great Gatsby (the one starring Leo D) as well.
So don't feel guilty the next time you plop down on the couch to do some tube watching-- just call it research and dig into some popcorn!