Open-Sourcing a Github Repo

open_source_repo

First and foremost: DON'T USE THE AMAZON MASTER KEY/SECRET
Use an IAM USER for each site/repo, with its own creds, so you can reset them easily and limit access

Secondly, use .env/secrets.yml--either using Heroku/Foreman, dot-env (Rails 3), or secrets.yml (Rails 4)
https://devcenter.heroku.com/articles/config-vars

Last thing, you'll need to scrub sensitive data out of your app's history (even if you reset/deleted those passwords, best to remove them from the history as well--you want to seem like a pro, don't you?)

https://help.github.com/articles/remove-sensitive-data/
https://rtyley.github.io/bfg-repo-cleaner/
http://stackoverflow.com/questions/4110652/how-to-substitute-text-from-files-in-git-history

Also, you should consider adding a license:
https://github.com/idleberg/Creative-Commons-4.0-Markdown