Maxum Anti-Fatigue Kitchen Mats from Wellness Mats
I have a Wellness Mat in my kitchen, and it has held up well for years. Anti-fatigue mats usually aren't cheap, but they pay for themselves as they ease strain on your back and knees during long hours cooking and washing dishes. I particularly like the Wellness Mat because it has stayed perfectly smooth and flat; the corners don't curl up, and it is still spongy and nice to stand on.
I especially like these Maxum mats, which have a more industrial look, and could work better in modern kitchens than some of the other styles.