To continue my recommendation of text-based games, if none of the ones I posted already grab you, I recently made a board for Enchanter, a fantasy text adventure from 1983. It's the first in a trilogy, the rest of which I hope to have up soon.
I'd like to recommend text-based games (or interactive fiction, or whatever you want to call them). As far as I know, I'm the only one actively running them, and I'd like that to change.
They're short—even at my slowest, I don't think I've ever had a run take more than 10 minutes. They're wicked fun and convenient to route and glitch hunt, since you can save and reload from any point in the game that you want, and you don't have to worry about any lacks or lapses in dexterity getting in the way of things. Your typing (or, for hypertext games, clicking) speed sets the pace, so you can start off slow and smoothly work your way up.
So far, I've run Anchorhead, Zork I, Trinity, Wishbringer, and Suspended. I'd love to see more runs on those boards.
I could continue to sing text-based games' praises as speedgames, but I'll leave things brief. If you have any questions about text-based games or speedrunning them, don't hesitate to DM me!