500 to NewPipe (dont know what I would do without them)
500 to Bitwarden (for hosting my passwords),
500 to XFCE (for the Wayland transition),
500 to Neovim (my text editor of choice),
500 for Aurora Store (essential for all Custom ROM users, to support them in these difficult times),
500 for the core Lemmy project,
500 for my instance's maintainers,
and last, but definitely not least:
500 for The Everything Project: A project which aims to provide a unified way to access various platforms and services including but not limited to Lemmy and other Fediverse platforms, Reddit, and more. (no, I'm not a contributor or maintainer, but if you want to be, or just want to find out more: https://github.com/everything-gripe )
uBlock Origin would be my number one, but they don't take donations. So my list would roughly contain:
Organic Maps
Thunderbird
Internet Archive
Codeberg
I'd like to donate to Firefox as well, but Mozilla spends too much for the wrong things and AFAIK it's not possible to only support Firefox development.
I recently donated to immich. That project created a product that allows me to take back ownership over my photographs and no longer am I dependent on Google for my memories.
Joplin. End-to-end-encrypted, markdown-formatted note-taking app that you can either sync using the cloud, Syncthing, or use entirely offline.
Kiwix since it allows accessing some services offline (Wikipedia, iFixit, StackOverflow) where Internet cannot be taken for granted. You can host a small Kiwix server than can be accessed as a local hotspot and browser whatever packages were downloaded into it.
Not my favourite but the most important:
A proper fully integrated clinical information system.
Currently all OSS are lacking behind seriously and especially the developing world but also rich countries would benefit so much from a proper system.
But sadly even that amount wouldn't cut it.
This is a topic that really needs money to safe lifes and safe money for everyone.
postmarketOS and the people porting Linux to phones
Panfrost devs
Nouveau/NVK
Yuzu (to get better Intel Arc support on Linux)
Libraries I use in OpenRGB
I already donate to one of the libraries I use on GitHub sponsors, also the box86 developer and a few others. I am donating to the UVTools developer as it was cheaper than paying for the shitty proprietary software subscription for my resin printer. I've donated to pmOS in the past as well as Debian and Arch.
A lot of the options listed in this thread are good choices - but most are big projects that get a fair amount of financial attention as it is (though very rarely enough to actually support the devs).
If I had $5k to donate to a project, I'd choose some of the really small FOSS projects that I use heavily, like AudiobookShelf
For me, I would definitely put the money into the open medical science stuff going on, like projects that are working towards open source insulin production and pumps and stuff. A close relative is diabetic (T1), and the things he buys just to stay alive are not cheap, and I would want that to change. The work those people are doing is extremely important, since insulin production is currently a very complex process and it takes significant time. Large Pharma companies have labs dedicated to doing it and they've streamlined the more traditional ways of doing it, which, due to the complexity, those methods have a very high (financial) barrier to entry, which keeps other, more generic labs from producing the substance needed for diabetics to live.
I'm talking about liquid insulin.
The FOSS push on this is focused on making a simpler method of production, and delivery of the insulin, giving third party and generic drug manufacturers an alternative to the high-cost of setting up a manufacturing line for insulin, and hopefully driving costs down.
They're also working on delivery systems, aka insulin pumps, that are FOSS. The problem there will be regulatory approval; the medical community is fairly strict when it comes to this stuff.... In any case, as nice as many things mentioned here are, I always feel that those guys always need help.
Easily the surface-linux kernel project, that level of dedication is incredible and without I wouldn't have my favorite laptop running linux right now.
And probably all of KDE's various developers if possible, since I both love the actual desktop environment and all the various tools they provide (like Elisa, Kdenlive, and KDE Connect).