Vanguard
Sometimes you don’t want to load up a spreadsheet to do these calculations by hand. I still keep my investments in Vanguard, but I have since started to diversify even more, as we will see below.
Fidelity
Charles Schwab
This is only a recent change since March of 2017, presumably because of the competition in the market, especially from robo-advisors who also charge minimal management fees. I plan on placing all of my future investments in Schwab.