Mutual funds, brokerage firms and many banks offer money market funds. Interest rates are not guaranteed so a bit of research can help find a money market fund that has a history of good performance. Popular CD maturity periods are six-month, 1-year and 5-year. Any earned interest can be added to the CD if and when the CD matures and is renewed. A CD ladder allows you to stagger your investments and take advantage of higher interest rates.