These links are for stuff that's useful, not just fun. This page is probably never gonna be done.

Downloaders

cobalt.tools: Video downloader, specifically doesn't work with youtube.
PasteDownload: Download videos from a shit ton of websites. They have a "Universal" option, so it might work if nothing else will? Haven't really limit tested it.

Programs and Codes

Calibre: File viewer that can read damn near anything.
Pagefind: A search function for HTML. I'm considering using this for my fan site.
WikPlayer: A music player for HTML, intended for blogs on Tumblr, Blogspot, and the like.

The Internet Archive: The GOAT. If there's something you want, you have a decent chance of finding it here. Do your part and back up your favorite things to this site.
BugMeNot: Shared account details so you can bypass login walls.
Catbox: 200mb or less file dump site. Good for music and audio files.
Empty Screenings: A lot of theaters sell only 1 or 2 tickets. Here's how you can find them in your area and get a theater all to yourself.
Kosmi: Remember Rabbit? If you don't, you know how you can sit in for Discord watch parties? This is that.

y2kid's TV Guide: EPILEPSY WARNING FOR THE ENTIRE WEBSITE, PHOTOSENSITIVE USERS PROCEED WITH CAUTION.