As Google have deprecated and are now decommissioning the Google Base APIs, and replacing them with Google Shopping APIs (see here) we found ourselves with a number of Ubercart sites with functionality likely to disappear (we use the googlebase module).
This sandbox module is intended to replace the Google Base API functionality with the new Google Shopping Content API (we don't implement the Search API here). The module also uses Google's new OAuth requirements for authentication.
As we're still in the stages of testing this module on a couple of our sites, it's not ready yet for prime time, but anyone willing to check our code and try it out is welcome to. Any bugs etc. we'll do our best to fix quickly so that this module can be published as a project.
This module hooks into Ubercart to pick up product data (it has a dependency on uc_product) and there is an 'extra' module to allow mapping of CCK fields to the Google product attributes.
There are a couple of hooks in there (implemented by the extra module) to allow the XML structure to be changed before sending it to Google.
For the moment we've only supported Drupal 6.x as we don't have any e-commerce sites on Drupal 7 and we're not sure yet how this is going to evolve.