Check out their sites, and you’ll see that each has ties to an array of retailers, restaurants and other merchants that offer rebates–all of which can be funneled into a 529 college savings plan (or some other savings account–you don’t need kids to join). Joining both is free, and the only cautionary note is not to count on them to put your newborn through Yale. Assuming a 7 percent return on a typical family’s spending, you might build up $20,000 or so over 15 years (at least enough for Psych 101 textbooks). Each plan also offers a credit card that gives an additional 1 percent rebate on all purchases.

There are many subtle distinctions between the two, but this one is key: you might get a bigger discount in many cases with BabyMint, but it requires more time at the computer to do things like download coupons or shop online. Once you sign up for Upromise, it runs largely on autopilot, crediting rebates based on your credit-card purchases with Upromise’s partners. But why not sign up for both? After all, it is free money.