Google Blogoscoped has a little more detail.
Update: Charlene Li points to a WSJ article that refers to Google Base as “the long-anticipated Google classifieds and listings service”:
The WSJ’s take is that this is Google’s assault on eBay. Others will be sure to look at it as a way to link classifieds and the anticipated Google Wallet. But I think it’s actually much, much bigger. Google’s main search index relies on spiders to crawl the Web and the much bally-hooed Page Rank system to understand relevancy. Neither work well in a database environment where pages are generated dynamically and linked pages don’t exist. I believe this is Google’s way to not only build a lucrative listings business but also to flesh out other areas like Froogle and Local with deep content that’s otherwise inaccessible or just plain doesn’t exist.
That seems a bit odd considering this snippet [emphasis mine]:
Examples of items you can find in Google Base:
• Description of your party planning service
• Articles on current events from your website
• Listing of your used car for sale
• Database of protein structures
Just what is Google selling here?