Before public launch, I found out that you could embed Puzzmo's puzzles. At the time, this was useful for testing out solutions for puzzles, since it wasn't easy to play a puzzle twice otherwise. After public launch, I thought it was a good way to share puzzles with people who otherwise wouldn't have access to them. It turns out, with the information you need to embed a puzzle, you can just give someone a link to it directly.
Stars indicate they're a confirmed Cohost user, since this list was compiled for a post over there.