What materials can be used as wicks?

What kind of common inexpensive materials could be used as wicks in a wick system hydro setup? There is no hydroponics store in my area so the material would have to be available from a hardware store... or walmart! The 'sea of green' setup will use 5" square pots... each will need about 15" - 20" length of wick material. Are there certain fabrics that should be used? I was thinking maybe a specific kind of rope perhaps... any ideas?

I am looking for wicks as well. Can someone please answer this?

the cotton rope from outdoor "tiki" torches are wicks.

you are right. I didnt even think about that.

common guys think, be creative! Any material that hold water can be used as a wick.