Just a moment ago Oceana moved my door sock and I told her to put it back. She had no idea what I was talking about, and finally I said, "The tube thing'y!" She hadn't seen it before, because I just made it last night.
I was sitting in the arm chair nearest the door last night and I kept feeling a breeze. I was right next to a window, so I thought maybe the seals weren't good. But when I checked, I couldn't feel cold are coming through the window. The only other option was the front door. I had suspected it would be an issue, because I can see daylight under the door and we haven't got a 2nd door. It's simply a front door. No storm door. I put my hand down by the base of the door. Aha! The culprit! The air was freezing down there!
I pulled out a piece of scrap flannel, ran over to my sewing machine that was still out on the kitchen table and sewed up a quick tube. It's about 10" across, and as long as the base of my door (I just held it against the door to measure). Sew the long side and one of the short sides. Fill it with... whatever. I wanted to fill it with rice, but I knew I'd be out of rice if I did that. Instead, I grabbed an old, stained bed sheet out of my extra linens and cut it into pieces. I pushed them down inside with a wooden spoon, packing as tight as I could. On the last few inches, I ran out of sheet, so I used a few crumpled newspapers. I turned the edges of the open end under, and ran it through the machine. It's doing the trick. :)
I turned it around this morning and felt the door-side of the tube, it's freezing! So I know it's helping a bit. I have plans to get some weather stripping too. But, in case you need to make one of these on the quick, there's the tutorial. This would be simple enough to do by hand too, if you don't have a machine. I'd recommend using something heavy to stuff it, not the fluffy teddy bear insides though, since it needs some weight to hold it tight against the door.
:) Hope that's helpful to somebody!