Check out series I savings bonds. You have to buy them directly from the Federal Government by opening an account @
TreasuryDirect - Home.
You are limited to $10,000 per person/ year, but you can buy them for your spouse/kids/grandkids, etc. They currently pay 3.5% interest. You have to hold them for at least one year, but can cash them any time after that. If you cash them before 5 years, you lose 3 months of interest. Principal is always safe. They will earn interest up to 30 years. Essentially zero risk.