Ask HN: References of open source “teaching” apps

I find the easiest way to learn a new language/platform is to get an example app running and mess around for a while - but it's often hard to find the right code for this. Is there a good reference of good example code bases?

For example, right now I'm learning Swift and looking for example apps. There are a bunch on Github, but I'm not sure which are best for learning. I could apply some heuristics like best commented / most watched, but seems like there should be a better way.

How do you all find example code bases to play with? If this is a problem for others, I'd be willing to put together a reference website for this - would anyone want to work on this?