Quick update on Proxigram: it now supports Flickr, Yahoo's popular photo sharing service. If you're a Pro account holder, it will even get realtime updates from Flickr, just like Instagram provides.
The "point" of the app has changed, too. The goal is to build a single API endpoint for all of your photos. While the photos will still be hosted on their respective services, you can now get one read-only API to see a normalized view of them all.
The project is still open source, so if you're looking for a sample node app that connects multiple third party services via oAuth (using passport.js), you can get the source on Github.
Facebook support is coming next. If you want support for your favorite photo services, please let me know what you want or, if you have the ability, submit pull requests with patches.
I've also written a few bits of supporting code for this. I abstracted out the basic PubSubHubbub verification calls into a standalone library: node-push-helper.
I also have stubbed out a new node Flickr client. I made a new one because I wanted to use oAuth instead of the deprecated Flickr authentication methods. After trying to retrofit one of the other libraries, I decided to just start over. I may merge this back into one of them, but for now, expect new functionality in the coming weeks. Here it is: node-flickr.
Would love code reviews and criticism from node experts. I know the code can be better.