I'm sitting here in the "Elevate your Force.com Platform Apps with the Google Visualization API" session at Dreamforce - given by Nir Bar-Lev and Itai Raz from Google, and Jesse Lorenz from salesforce.com.

It's pretty interesting - the Google Visualization API has a tremendous number of visualizations available, including tables, stacks of cash, heat maps, funnels, timelines, line charts, gauges, bar charts, word clouds ec.

What's nice is that the API is a web-based service, and so you can use it in your own Force.com apps to visualization data. More exciting, is the new Code Share project Force.com for Google Visualization

Using the toolkit is pretty simple as they make everything available as a Visualforce component - for example you can simply embed something like this on your Visualforce page:

   <c:TimeLine jsondata="{!SalesActivity}" 
                width="900px" height="300px" 
                displayZoomButtons="false" 
                zoomStartTime="new Date(2008, 07, 01)" 
                zoomEndTime="new Date(2008, 09, 30)" 
                colors="'#C2CD23'" />

You controller will do the query for the data and return it - in this case in a getSalesActivity() method.

I see that there are components available for bar charts, line charts, gauges, line charts, column charts, time lines and data tables. If you're keen to get your hands dirty and extend the integration, just contact the project owners and add more components!

For more information, check out Jesse's blog post about the toolkit, the wiki page that describes the technology, and of course the Code Share project itself.