A few CDs (preferably of the same color)
White cotton lace
You can use any old CDs which have gone bad, but this looks best with plain gold or silver CDs.
Don't cut the cotton lace before starting.
All you have to do is take the CD and spread some glue all along the periphery of the CD. Then take one end of the lace and start sticking it onto the edge of the CD, making small pleats as you go all around. When you've finished, cut the lace and you have the coaster or table-mat ready! If you wish, you can even add some lace in the middle.
These coasters will look very pretty, and are even double-sided. They even retain heat well and can be used on the dining table easily.