Google just released "Google Merchant Center" -- a service that they want users to use instead of Google Base for products. If you have product data in your Google Base account, you should automatically find all your stuff available in the new service.
Previously, you may have used Google Base to upload and manage Product listings. Google Base is still available for other types of structured content, but the Google Merchant Center provides a better, optimized experience specifically for merchants. The Merchant Center is where we'll continue adding features and improving the tools for uploading and managing product listings.
It's hard to tell if Google is actually thinking of pulling the plug on Google Base or not -- I'm thinking they are going to let it die a slow death. The reason I think that is because they are actually replacing their Google Base Blog with the Google Merchant Blog.
As part of the launch of Google Merchant Center, this blog will be replacing the Google Base Blog. Please update your bookmarks and subscriptions, and visit us often!