GitHub is probably where you should start—honestly it's pretty much the default at this point. Millions of repositories, most of it people just dumping their code. Yes, a lot of it is unfinished projects someone gave up on after 2 commits but there's gold in there too. Search is mediocre (lacking in some ways, very spammy in others) but if you know what you're looking for or at least have the right keywords you can find working scripts for pretty much anything. CLI tools, automation scripts, web scrapers, Wordpress plugins, browser extensions, you name it. And you can see the commit history so you know if it's actually maintained or if the last commit was in 2019 which—spoiler alert—probably means it's broken now.
SourceForge was huge before. Before GitHub basically. Still has lots of downloads but a lot of it is older stuff nobody moved off there. It's not where you're going to find new shiny scripts but if you're looking for something specific and/or old (some old Python script for some data manipulation no one uses anymore or whatever) you might find it archived here. Kinda dated UI, very early 2010s energy here, and their download process is garbage (lots of ads and redirection pages) but the library of content is actually massive. Be wary, some of the older projects haven't been touched in a decade so some things might not even work.
Stack Overflow doesn't really host full scripts but... hear me out. Code snippets people post in their answers to questions. Very often it's exactly what you're looking for. Someone asks "How do I scrape dynamic content using Selenium" and then five different people post full working examples in the thread. It's not a nice .py file you can download and run but copy paste works and you often get some useful context (versions they tested on, which dependencies you need to have, common problems) and low-key one of the most useful resources despite the fact it's not a script hosting site but a Q&A site.
Greasyfork is the userscript home. Userscripts are those small JavaScript programs you run in your browser that make websites do stuff they don't normally do. Need to auto-skip YouTube intros? Block some popup ads on one specific site? Add new features to reddit? You can find a userscript for it here. The UI is very clean, everything is sorted by categories and ratings, installing is super easy if you have tampermonkey or greasemonkey. Quality control is wild (some scripts are amazing, others barely work or have been abandoned by the author) so always check the reviews and recent updates before installing.
GitLab is GitHub's main competitor, but honestly? Pretty similar. There are some little quality of life differences that I personally prefer on GitLab (better for hosting private repos for free for example) but nothing game changing for the most part. The community isn't as big but there's still a ton of good projects there. Especially stuff that has been migrated away from GitHub by people who got salty about Microsoft now owning GitHub. Worth checking if you can't find what you need on GitHub because some projects are only on one or the other.
Bitbucket is another git-based code hosting site. Kinda gets relegated to third place after GitHub and GitLab for the most part. It's a bit more focused on being used by professional teams (tons of integrations with Atlassian products like Jira) but there's also a ton of open source repos you can search through. The discovery of public repos isn't as easy here (their search and trending features are very barebones) but if you already know the name of a project or someone sends you the direct link to it it works fine. Not a starting point but a valid option.
Script Slug, on the other hand, is a bit more niche. They are more about offering production-level scripts broken down with analysis and commentary. It’s less of a grab-and-go PDF and more of an instructional, as it were. If you’re trying to learn, as opposed to just browsing and having fun with scripts this is an absolutely fantastic resource. They break down scripts from all genres, as well as offering useful information about the films and shows, how the screenplays were written, and so on. Again, more instructional than archival, but if you’re trying to improve your craft this is way more useful than just passively perusing scripts for fun.
And finally, if you’re after something really out-there, or foreign films in particular, your best bet will really be just…googling it. “title of film” plus “script PDF” or “screenplay PDF” or whatever and you’re bound to come across at least a few leads. WordPress blogs with random downloads, Google Drive documents, Reddit threads…there are a million sites out there where people will host scripts that didn’t make it into one of the big archives. It’s hit or miss, but if you’re searching for one specific script this may be the way to go. But be careful. These links can be sketchy, so my best advice is to only click direct PDF links. If a link says you need to download a file to read a PDF, or you need to create an account on a site, move on.
One final note: if you want truly “industry level” samples of formatting (WGA standard, in other words) then you’re going to need to look at the WGA’s own script library. Membership is required, though during Awards consideration season (aka every year when the Oscars are near) they will post sample scripts that are made public during that time. It’s basically as close to straight-from-the-source as you can get, other than, you know, working for the industry.