I-Bonds are savings bonds issued by the U.S. government that pay about 1.35%. This rate is much higher than any money market account. You must keep your money here at least a year and no individual can contribute more than $10,000 each year. You can also put in an additional $5,000 if you invest your tax refund. If this is money you want to keep safe and not need for 2-4 years you should check out this site. https://www.treasurydirect.gov/
The I-Bond will adjust every 6 months to the CPI. This is a perfect inflation hedge for short term cash.