This is an unusual investing app: Acorns is free for iPhone; you connect your credit or debit card account to the app and, anytime you make a purchase, it invests your “loose change” into a diversified porfolio. (Buy lunch, for example, for $12.50, and the app will round that amount up to $13—using the 50-cent difference for the investment.) You can also choose to directly invest funds in amounts of your choosing. Acorns charges $1 a month, plus annual management fees, once you’ve started investing. Will microinvesting yield big returns? Only time will tell.