Want to save more money? There's an app for that.

There are dozens of ways you can save a little extra cash each week, from having part of your paycheck automatically transferred into your savings account to skipping your morning coffee once or twice a week.

But what's even better than saving that money is investing it. Even the best high-yield savings accounts will only earn you around 1% annual interest, whereas you could earn an annual rate of return of around 7% by investing that money instead.

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When it comes to investing, though, many people don't know where to start. When they hear the word "invest," they picture images of Wall Street and stockbrokers managing millions. Anyone can invest, though, even if you only have a few dollars to save. And you don't have to invest just to save for retirement -- you can save for the down payment on a house, your child's college tuition, or even that trip to Hawaii you've always dreamed of taking.

You also don't have to have thousands of dollars already saved to start investing. While some traditional brokers do have higher minimum account balances, there are several apps that make investing easy and inexpensive while still helping you grow your savings.

1. Acorns

Acorns is made specifically for people who want to save extra cash without the hassle of managing their investments. The app works by syncing to your credit and debit cards as well as your bank account; then it rounds every purchase up to the nearest dollar and invests the difference.

So, for instance, if your grocery bill totals $34.05, Acorns will round it up to $35 and invest the $0.95 automatically. It may not seem like a lot, but it does add up. Even if you're only investing $2 per day, for example, assuming you're earning a 7% annual rate of return, that amounts to about $754 in one year. After five years, you'll have earned over $4,300 -- just by rounding up to the nearest dollar. You can also choose how aggressively you want to invest to ensure you're only investing what you're comfortable with.

The pricing model also makes it easy for anyone to start investing. It costs just $1 per month, and once you have a balance of $5,000 or more, you'll pay 0.25% of your account balance.

While Acorns makes it easy for novice investors to save, that's also one of its downsides. Because it's made for beginners, it doesn't offer as many choices as other brokers. For example, it only offers individual non-retirement accounts (so you can't use Acorns to fund your retirement), and it doesn't offer any support from human financial advisors to help you talk through your investment strategy.

2. Betterment

Betterment is like a more advanced version of Acorns that's made for people who are still new to investing but are more serious about it than someone who's just looking to save a little extra cash.

Like Acorns, Betterment is completely automated and will invest your money for you after you take a short quiz to assess your comfort with risk. It also offers traditional IRAs, Roth IRAs, and SEP IRAs, and you can roll over any existing retirement account to Betterment.

Relatively low fees make it an affordable option for people who are just starting out. The basic plan has no minimum required account balance and charges a fee of 0.25% of your total balance, while the premium plan charges a 0.40% fee and requires a balance of at least $100,000.

The main advantage of the premium plan is unlimited access to a Certified Financial Planner who can give you personalized advice to make the most of your money, although the basic plan also offers access to advisors who can answer basic financial and investing questions.

Betterment is designed to help you reach long-term savings goals, such as saving for retirement, a house, or a new baby. While that doesn't mean you can't save for short-term goals -- like a vacation or concert tickets -- it may offer more features than you need if you're just looking for a simple savings app.

3. Robinhood

Robinhood is a zero-cost investment platform that makes it easy to get started investing, but it also offers more advanced features at a relatively low monthly charge for people who want greater control of their investments.

Like Acorns and Betterment, Robinhood is an online-only broker that syncs to your bank account to make depositing money easy. The difference is that Robinhood is a far more hands-on app that allows users to choose which specific stocks and exchange-traded funds (ETFs) they want to trade.

This app is great for investors who want to take investing into their own hands without the high fees that traditional brokerages typically charge. Robinhood charges no trading fees or commission, while even the least expensive traditional brokerages charge anywhere from $5 to $15 per trade.

Saving money is a challenge for many people, so if you're struggling to invest in your future, you're not alone. Fortunately, technology makes it a little bit easier. Whether you want a completely passive way to put your spare change to good use, an easy and inexpensive way to start saving for retirement, or an affordable, hands-on investing option, there's an app for that.

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