We always keep the cards we are given and use them either to make new cards or gift tags. Gift tags are really easy as you just cut up the main picture and punch a hole at one end. Then you can tie it on to your gift using the gift tape or string round the parcel and write a greeting on the plain side on the back.
Christmas cards can either just be the old motif stuck on a new piece of card or for children we tend to do something like the above. This one was made a few years ago and uses fingerprints from the children, ideal for grandparents.
I know that lots of people like to buy charity cards and we have done that in the past but now we do homemade ones for recycling and give the money we save to charity instead.