All server software. No one makes money from FOSS desktop software.
Depends what you consider making money to be.
Plenty of businesses depend on FOSS desktop software, it makes them money. If I use Linux and tools like Blender, Vim, GCC, etc..., and I sell the resulting product, then I'm making money with FOSS, am I not?
You are, but the guys coding the software you use are not.
So unless you make the effort to contribute back, they will have some issues to pay the rent.
Firefox?
Of course there is Google, Amazon, Red Hat, SUSE, even IBM uses a lot of GPL software...