For other repos, Elixir and Phoenix both have "topics" on github now so you can filter a search by repos which are tagged with those topics and order them by stars (obviously this does not sort the wheat from the chaff or the libraries from the projects though). [3]
Welcome to the community :)
[1] https://www.kickstarter.com/projects/1003377429/firestorm-an...
[2] https://github.com/dailydrip/firestorm
[3] https://github.com/search?o=desc&q=topic%3Aelixir+topic%3Aph...
Even so, I find myself having the exact same issue as you are having when using Phoenix and Ecto. The way I like learning something new is by looking at something someone else has made. This gives me a much better view of how things are done than just reading getting-started guides and docs. I have looked, but I haven't found a lot of examples that actually applies to the latest versions of Phoenix and Ecto.
It's a simple, repeatable process that gets you through the basics of the architecture across the board. You'll get a couple of routes, a couple of controllers, a little bit of database access, a bit through the view layers and by the time you're done you'll have a simple app that you can experiment with. It's generally my go-to "learn the language" process for anything.
I didn't open source it, but here's a little write up on mine.
http://www.brightball.com/articles/insanity-with-elixir-phoe...
Take a look at the Building Umbrella Project from elxirconf: https://github.com/poteto/elixirconf-201620 by Wojtek Mach.
The source: https://github.com/wojtekmach/acme_bank22 is a great example of an umbrella app. For example, he uses two instances of phoenix (backoffice and bank_web). It's a working app, so you can experiment with it too.
The talk is here: https://www.youtube.com/watch?v=6NTmUQClHrU18 I found it very instructive.
https://github.com/poteto/elixirconf-2016