Additionally, if you live in a city in the U.S. that being with "Chip," you can also get free dip.
If your name is "Chip," you can claim your free dip at www.EveryChipGetsADip.com by submitting a picture proving you're a "Chip." Even if your name isn't "Chip," you can still participate in the promotion by turning yourself into a chip by submitting a picture of your face and following the instructions at www.faceinhole.com/Tostitos (so named because the site basically sticks your face carnival style over any number of different chips).
Also if you live in a "Chip" city like Chippewa Falls, you can also upload proof that you live there to score a free dip.
As to the idea behind the promotion: According to Jeff Klein, Vice President of Marketing at Frito-Lay North America, "We all know that chips and dip go together perfectly, but we began to wonder if we were somehow neglecting some of the most important Chips out there. So on a day called National Chip and Dip Day, we couldn't help but wonder … isn't it about time all Chips get their dip?"
The offer runs through Monday, March 23, 2015. You can find more details regarding the promotion at www.EveryChipGetsADip.com.
If you're more the audio-visual sort, here's a quick video explaining the promo: