The iShares Treasury Floating Rate Bond ETF (NYSEARCA:TFLO) invests in floating rate treasury notes. These securities are similar to t-bills, with functionally identical risk and volatility, but slightly higher yields and returns. TFLO's low volatility and good 5.6% forward yield make it a fantastic cash alternative, and a buy. TFLO invests in treasuries with variable interest rates. Rates are reset weekly, and are (currently) equivalent to 3M t-bill rates plus 0.245%. Higher t-bill rates mean higher rates for TFLO's underlying holdings, and for the fund itself. Interest is paid quarterly. More details here.