In my family we will never have an actual need for a trivet - and if you've ever met my Grandma you know why, as I'm sure you've received your lifetime supply of her made-with-love pot holders. So as you can imagine, if we need a trivet, we just use one of Grandma's mass produced creations.
That being said, if you aren't an heir to Grandma's Potholders Inc. here is an easy way to make yourself your very own trivet:
Decorative tiles can be picked up from hardware stores such as Lowe's or Home Depot for practically nothing. Or you can do as I did and paint your own! (My favorite place to go is in the U Village, called Paint the Town. Check them out: http://www.ceramics-painting.com/works/.)
Lastly, simply cut a felt square to size and glue to the back. And there you have it! A trivet!