The main funders are LTFF, SFF/Lightspeed/other S-process stuff from Jaan Tallinn, and Open Phil. LTFF is the main one that solicits independent researcher grant applications.
There's a lot of orgs, off the top of my head, there's Anthropic/OpenAI/GDM as the scaling labs with decent-sized alignment teams, and then there's a bunch of smaller/independent orgs:
And there's always academia.
(I'm sure I'm missing a few though!)
(EDIT: added in RR and CLR)
Very surprised that you don't have a regranting budget! I don't know which funder I would expect to do that, but I would've expected this to be more common.
I guess Jan Tallinn does this, and Manifund does this. Hmm.