MailChimp OAuth2 library for Django
github.com
github.com
Super-simple but it works.
Demo app here: https://github.com/kennethlove/Django-MailChimp-OAuth2
So now they can use their account and your app and everything is hunky dory.
I know that's pretty general and all, but that's how you'd use it. MailChimp is trying to move away from API keys and all that 'messy' authentication and toward OAuth2.
I do a lot of development with Django and MailChimp, but most of it is for implementations against a particular account -- so it's a lot easier just to stick the API key in a settings file and skip the OAuth stuff.
The OAuth2 service is aimed at people building apps for people that use MailChimp, not people that subscribe to a mailing list hosted on MailChimp.
Like how you'd use Twitter's OAuth2 service to build apps for people that use Twitter, not those that just read feeds.