An example of base product is iGoogle that lets you add mini-web application to a web page. Google made it easy for developers to build gadgets, but it didn't manage to enable users to build their own gadgets. iGoogle Gadget Creator is a very basic tool and should be transformed into a powerful wizard that lets you add content from the web.
Another great base product is Google Maps, which provides a great framework for integrating geographical content. Developers used Google Maps API to create a lot of mash-ups and Google wanted to add these mash-ups back to Google Maps. Mapplets and personalized maps were the products that made this possible. Unlike iGoogle, it's much easier to bring your favorite content to Google Maps and this platform will generate a lot of interesting things when Google will transform personalized maps into wikis, by enabling collaborative editing.
I think we'll see many web pages created on top of Google's base products as they become great ways to gather and organize information. Here's a great story from Jess Lee, product manager at Google Maps:
On Tuesday [October 23], we saw a huge increase in traffic on Google Maps. The traffic spike was so large that our servers thought they were being DoS attacked. It turned out that the additional traffic was due to hundreds of thousands of people constantly refreshing maps about the terrible wildfires in Southern California. Several news outlets and individuals had used the My Maps feature to create maps that tracked the spread of the fire and included information on evacuation alerts and evacuation center locations. (...) What's truly amazing and surprising to me about all of this is that the most authoritative source of information on the wildfire was produced by a tiny broadcasting station like KPBS and that this information was disseminated online using consumer-facing tools like My Maps and Twitter. I would have expected a government agency or a large traditional media outlet like CNN to have been the primary source of fire maps, but a lot of them just linked to the KPBS map in their articles. In fact, Calfires.com (the official fire website maintained by the governor's office) simply embedded the KPBS map on their homepage using Google Maps' embed feature.
And here's the KPBS map.