Vikram Vaswani have written an interesting article over IBM developerWorks on processing and integration of Google Notebook data with PHP. In the article, the author explains how to use the Google Notebook REST API to build PHP-based client applications.
php-notebook

Google Notebook is a free service that allows users to save and share notes and Web clippings in an online journal. A REST-based API allows developers to build customized PHP applications around this service using SimpleXML. In this article, you learn how to use the API, with examples of reading notebooks and notebook contents using PHP.