You all have the best ideas.....

When my mat gets too ancient I cut it in half which means I use another section to cut on. Finally when it gets to be A4 size, I get two pieces of thin hardboard layer some wadding (batting) on one side of each and then cover with some fancy fabric - this joins them together like a book. Glue the fabric down on the other side from the wadding. Then on one "page" stick a sheet of fine sandpaper (which should cover the folded over fabric edges) and on the other "page" stick your A4 cutting mat. The "book" should have a narrow "spine" so that you can fold the two "pages" together when its not being used. Great for applique work or piecing on your lap in front of the TV, and also for workshops.

I know of a person who laid her warped mat on the hood of her car when she drove into her garage, placed some weight (books, I think) on the mat, and let it cool with the car. Like new mat.

I got to the bottom of the first page of replies and saw that everything I've done with them has already been suggested: husband's workshop, purse bottoms, templates...

This board is wonderful. So many clever people here! Just amazing, you all are!