Like all things Google - Goolge Feed API is now deprecated.

Google Feed API - demos

I've been playing around with GoogleFeed API for quite a bit! Here are a bunch of different examples.

1. Card Based Feed Display
2. Multiple RSS Feed Page
3. Multiple RSS Feed in Material Design (Using Material Design Bootstrap - https://github.com/FezVrasta/bootstrap-material-design )

To know more about the Google Feed API - check the dev guide at https://developers.google.com/feed/v1/devguide

The AJAX Playground is not available any more and redirects to Google API's explorer - http://code.google.com/apis/ajax/playground/