I was actually just looking at a job posting at the Simons Foundation, which makes its omission that much more embarrassing. The Schwartz Foundation also paid for some stuff (and a lot of pizza) in grad school,so I should give them a nod! CZI and Simons/Flatiron have their own buildings. I think GBM and Sloan are more grant-making organizations.

There's also DE Shaw Research, which is particularly interesting since the billionaire in question works there himself.