In an effort to prevent some drafts, I have started to use these:
Yup, that foam stuff you wrap your pipes in. It slides right under the door filling in the gap between door and floor! If your going to go out and buy some foam insulation, you may want to measure your gap first. I used what I had on hand and it worked out ( luckily) and then got some hand me down foam thats a little thinner, it still worked for a different door but if you have a big gap, and buy the thin stuff your still going to have a gap!