Do these work well? The draft guards (fabric ones, not the ones that they attach to the doors) that they sell at stores that you put just on the inside of the door what do they call those?

Draft dodgers.

Yes they work and you can make them easily.
http://www.ehow.com/how_2195787_door-draft-guard.html

http://www.craftbits.com/project/door-draft-stopper

http://tipnut.com/draft-stoppers/

i used them in a house i had years ago, very helpful

If you are talking about the ones that slide under the door then I can say YES! They work very well. Everytime the wind would blow my front door would howl and my apartment sounded like it was haunted but now I can't tell if the wind is blowing.

There's some real cute ones that you can make that look like a doll doing the splits ... or an animal, etc.

Yes they do help.

I even use them to block off rooms that I don't want to heat or cool in my house. Very effective!

I bought two draft dodgers at Home Depot and will use them when it gets cold. A rolled up cheap throw rug or towel would work too. I just put them on the inside of the door.