I support KDE, Mozilla and a fediverse instance currently. A small amount to each, each month, but it is worth it to me. I pay for VPN, email, and password manager, so contributing to KDE, Mozilla and the fediverse feels just like another small set of subscriptions.

I'm lucky I can afford to do this; I think any financial contribution of any size is appreciated by the FOSS world.

EDIT: In terms of things I'm thinking of - Jellyfin and maybe Piefed. Mozilla is a bit of a question mark for me with the AI stuff; but I still value Firefox immensely.