I'm at Fidelity. I've got mine parked in Fidelity's Government Money Market Fund (SPAXX). This is the default position at Fidelity. Mostly US government securities it had a recent 7 day yield of 1.96%
There is also the Fidelity Prime Money Market Fund (SPRXX). Mostly invests in CD's (36%) and financial company's commercial paper (31%). It had a recent 7 day yield of 2.08%.
Moving into a little more risk, there is Fidelity Conservative Income Bond Fund. Recent 30 day yield of 2.29%. Basically ultra short term corporate bonds (mostly from banks) that are rated:
AAA...1.4%
AA....25.4%
A......35.1%
BBB.. 4.0%
Next move would be a low duration bond ETF, like Fidelity's FLDR. Had a recent 30 day yield of 2.66%.
Thinking I should be at least in Fidelity's Prime Money Market fund, SPRXX, but why not squeeze out a little more return with the next couple of options?