"When users search for products on Google.com, the system will present them with another search box so that they can refine their query. After users refine their queries, Google takes them to a second page populated with product results from the Google Base listings service."
Google also plans to diminish Froogle's importance and to include ads in Google Base. Google recently redesigned Google Base, removed the search box from the homepage and added the tagline "Post it on Base. Find it on Google" to show you'll see more search results from Google Base on Google.com.
You can already see this integration if you search for "jobs" (it works in the US and in few other countries).
In the future, you'll search for a product like "dress" and customize its characteristics before actually seeing the search results.
It's important to note that Google ranks the results from Google Base according to their relevancy and using the metadata attached to each item. Listing products in Google Base is free.
When it was launched, Google said that Google Base is a service that collects information not yet in Google Search, but the real idea was organizing this information and making search results more intelligent using it.