Where to start with Google Reader as an API?

Question

I want to build a widget for WordPress that simultaneously displays my latest Google Reader items on the front page and allows for management from behind the WordPress dashboard. I can already add my "shared" items using code I've found in various Google searches, but that's not exactly what I'm looking for.

I like the functionality of the Google Reader widget in iGoogle, and I want to replicate that on the WordPress dashboard and build a read-only version for the WordPress front-end. Where do I start in the API (public or 'unofficial') to get this built?

-- Update --

I've found some limited documentation regarding authentication protocols, but I've been unable to implement anything. I can parse a URL to authenticate and get an SSID that works when directly placed in a browser, but both GET and POST requests fail via PHP, so I can't get any further than that.

-- Update --

I've converted the first few steps of Martin Doms' C# tutorial into PHP for anyone who's interested in doing this on their own site.

Answer 1

Here's a nice 3-step tutorial: http://blog.martindoms.com/2009/08/15/using-the-google-reader-api-part-1/

If you're having problems from PHP, then I think you should post the PHP code to see where it's failing. These steps should work flawlessly.