Mastodon is one of the most well-known federated social platforms. If you're on NeoCities, there's a chance you know about Mastodon as well. If not, you're now aware of its existence.
If you want to socialize with people over the internet in the already familiar format but don't want to support Big Tech and/or want more control over your data and improved privacy, this is a great fit for you! The best way I can describe Mastodon is "Twitter but better in every way." But a better way to describe it as as towns or villages. This video explains it far better than I can, so give it a watch.
There are a few clients you can use to interact with Mastodon instances.
You can just use the web client. Just go to the instance's website, login or sign up, and you're in!
This is a client you have to download on your computer. You can see its Github repo here. It's an ok, client if you like Tumblr's tiled layout. Other than that, I don't think it's that good of an option. It hasn't gotten any new commits since January 7th, 2021 (as of the time of writing) and the UX is trash. When you reply to or create a post, it goes back to the top instead of staying where you were. Another issue is when viewing people's profiles, the bio isn't displayed correctly. It's displayed as if it was a single long line. I doubt these will get fixed since, as already mentioned, Hyperspace doesn't seem to be actively developed or maintained.
This is a vastly superior client when compared to Hyperspace. You can find its Github repo here. The UX is better because it doesn't go back to the top when you reply to make a post and it allows you to customize the color of many elements and profiles are displayed properly! It's also being actively developed. If you want to use a desktop client to interact with Mastodon instances, opt for Whalebird! The only downside so far is that you can't launch it with a --hidden option like Element. Once this is added (if ever), I will never go looking for another client.