Here is a link to the info you need to know about getting into Google Shopping a.k.a. Google Product Search
1. Upload your products through the Google Merchant Center
You can upload your products with a data feed. You'll be taken to the Google Merchant Center to submit your product information.
2. Users find you on Google Product Search
Your products will appear on Google Product Search and may be displayed on Google.com. Your store and products will be shown to shoppers when they type in search terms relevant to your product offerings. Shoppers simply click on your listing to be brought to your site.
We currently provide several options for you to submit your product information to us.
We recommend creating a data feed which contains all of your content in a single tab-delimited text or XML file. You can send us your data feed directly through your Google Merchant Center account, or by using File Transfer Protocol (FTP).
The Content API for Shopping is designed for developers with technical know-how who would like to integrate their applications with Google Merchant Center. Your application can upload new data, update or delete existing items, and query Google Merchant Center data to find matches for complex attribute criteria. The Content API for Shopping uses the same underlying protocol as the other Google Data APIs.
Learn more about using the Content API for shopping.
You may also submit products through a Google Product Search Partner, or through a Google Marketplace Partner.
Is any of this still relevant after the current Google changes to paid featuring?