This looks really useful. Google recently released an API for using Gadgets and visualizations inside of (or pulling from) the Google Docs spreadsheet system. Developers can create useful visualization models, like Gantt charts or geographic heat maps, and Docs users can use these tools inside their own documents.
The Gadgets in Docs framework also allows the visualizations to be plugged into iGoogle, so you can have an up-to-date visualization data on your iGoogle page that pulls from spreadsheet data in real-time. I found the timeline gadget, pictured above, to be particularly useful, but if you don’t find the particular visualization you need, you can now go ahead and make it yourself.