Asklemmy

For both professional and personal use, I can list 2 that you likely haven't heard of:

https://github.com/meowtec/Imagine Imagine PNG/JPEG optimization - it basically compresses images and photos so you can email lots of stuff back and forth without using the likes of WeTransfer.

https://ditto-cp.sourceforge.io/ Ditto Clipboard Manager - a multi clipboard for Windows. Ever try to paste something, only to realise you've already copied over it? Its use and helpfulness is so ubiquitous, I just could never live without it anymore.

Visual Studio Code

Cura

Blender

WINAMP + GOLDWAVE!!!!!

I don't know if this will show up or is already in the list, but: Rufus. I burn all my thumb drives for os installs with Rufus. It also lets me bypass a lot of the windows garbage that they've tracked on to the installer, like making you sign in to a Microsoft account to install. Also, Ventoy. It's a multiple OS installer, so one big thumb drive lets me install any number of OSes from it.

While I'm setting up those OSes, ninite gets me my windows programs, and Snappy Driver Installer Origin gets me my drivers. No more laptops with pre-installed bloat for me!

ReadEra is a great freemium ebook reader that got me back into reading again.

Ffmpeg, VLC

Bitwarden - been using it for over 5 years, such an amazing utility.

Proxmox and OPNsense. Blows me away that I can get that level of functionality completely open source.

Tailscale's free tier is unbelievable.

As a Mechanic. Ampol Netlube, from lawn mowers and passenger vehicle to motorcycles and heavy mining/industrial equipment, I can find how much lubricant it take, what viscosity and specifications.

ShareX. The ability to screenshot or record a video of practically anything onscreen with any shape or form, assign hotkeys to certain tasks, and the ability to automate all of that and attach to other applications/processes for a smoother workflow? For free? Count me in.

Rclone, Neat Downloader, VLC, FreeCommanderXE, LMMS, any Keepass program, Rufus, Gimp, Notepad++, 7zip, ffmpeg, yt-DLP

https://heldercorreia.bitbucket.io/speedcrunch/

ViMusic and Firefox. Both are open source

Bit of a different answer, but I enjoy Daylio. Very simple and easy to track your mood and activities to look back on. Not really super useful, but very interesting and fun!

Here's how you actually free space on your computer in a way that matters without installing some malware "fix-it" program or need a computer divining rod to find every random file:

• WizTree: Scan your entire computer hards drive(s) in a matter of seconds and display a very useful graph and data about where your space it being taken up. It's eons faster and easier to use than the leading competitor WinDirStat to the point where I can't imagine why anyone would use something that isnt WizTree.

• BCUninstaller: It helps uninstall as many apps and programs off of your computer automatically with little to no user interaction needed beyond hitting the "start" button

• BleachBit: It deletes all the temporary and nonessential stuff that gets accumulated over time. It won't clear as much as BCUninstaller or deleting stuff with WizTree and a lot of apps will generate most temporary files again anyways but I do typically see a decrease of around a gigabyte or two. Worth a shot in any case.

• Winget: While not a software in the general sense, Winget is a package manager built into Windows 10/11 itself that lets you automatically download, configure, and install a ton of programs in one command via command prompt or PowerShell.

Every single program I've listed here are available on Winget.

So much software is so necessary that I cannot believe it is NOT free.

Definitely R/R Studio if you're in data analysis. Runs circles around commercial Software in terms of scope and customization. A little harder to get into of course, but once you get the hang of it, there's little you can't get done with it.

BOINC. If you're a scientist, you can use it to distribute massive computational workloads for free. And there are tons of computing volunteers who will gladly do the computation for you. If you love science, it's a great way to engage with some cutting edge research projects and know that you're "doing my part!". You can help research cancer, develop new open source drugs, map the galaxy, or just do some fun math stuff. Just install and pick your projects, no PhD required! There was even a projects for a while to reverse all the minecraft seeds that some people participated in. https://sopuli.xyz/c/boinc

Umm... Lemmy.

Libby, the ebook reader app that is synced with my library card! It works quite well, and though I technically pay for my public library via taxes, the app is free and fantastic!

ffmpeg, imagemagick, povray, supercollider, blender ...

I'd also say amule, qbittorrent, fopnu (freeware, but not free), retroshare.

There are likely many others. EDIT: ... I can't quickly remember.

DaVinci Resolve

Jerboa

ReVanced and SmartTube. Google would have been able to justify their premium subscription much easier if they had all of the features from both.

Any web browser

SmartTube for Android TV, avoid paying YouTube Premium with no ads and SponsorBlock.

Duplicati. It just works. Paired with Backblaze (not free) it's been our default home backup for a long time.

DMDE. I know they have free and paid version. Even with the free version I was able to recover 500gb of data 100% with all the folder structure intact. With the free version you will have to manually select each directories but it was worth the effort.

Also Mega. I have multiple legacy accounts that has permanent 50gb space.