SGOV - my growing cash position at Ameritrade, which they were paying me a meager 0.35% annualized on, led me to search for a short term treasury bond ETF last week. I found it with a google search and promptly began shifting cash into it ..... now almost all my idle cash is in SGOV. It's got great liquidity with a very tight 0.01 bid/ask spread so I'll be moving cash in and out of it as needed.