I found great interest in the charting solution recently proposed by Claudio Cabaleyro (and relayed on endusersharepoint.com).
Claudio had the smart idea to leverage the SharePoint grouping feature, to collect the data needed for the chart. One advantage of this solution is that the script is generic and can be applied as is to any list.
Note that the initial solution allowed only one list per page. See updates here and here to deal with multiple lists.
One limitation is that the solution relies on Google charts, which means that your data is going to travel over the Internet. This is fine for public information, but not suitable for secure data.
So I adapted Claudio’s script to make it work locally, using a charting tool. Here is a first demo:
http://www.pathtosharepoint.com/Pages/BlogsMap.aspx
I have already mentioned in previous posts several third party Flash/Silverlight/JavaScript charting tools. My favorite is FusionCharts, as it offers the largest range of charts. For this demo, I am using FusionMaps v3. The map is based on a flash file stored in SharePoint. It pulls data from the SharePoint list on the right (Claudio’s method), then adds color coding based on the value.
I have partnered with FusionCharts, and in the months to come you’ll see more demos and tutorials that showcase their products. The charts come in two flavors, the complete v3 version and the free v2 version.
Path to SharePoint... and Beyond! 
Hi Christophe
I’ve been using Fusion Charts too for some graphing – Google was no good for me due to the mix of https / http (Google charts are only available over http) plus the security implications.
I combined it with a data view that totals the occurences of certain values in a list and graphs it as a neat pie chart.
Look forward to your demos too!
CHeers
Ben
Thanks for the link Ben. Is there a tutorial that comes with your demo?
Not yet!
Christophe – I’d like to add FusionMaps to the Charting and Graphing SharePoint workshop. Where can I download v2 so I can distribute it to students? Thanks. — Mark
Mark, you can find the link on the following demo page:
http://www.pathtosharepoint.com/FusionCharts/default.aspx
In the right column, click on “FusionCharts Free (v2)”. On the FusionCharts Free page, under links, you’ll find the charts gallery, the download section and the terms of use.
Do you have an example of how to put the data source from a list
I don’t, all the pieces are scattered across several demos. See for example my image rotator as an example of how to pull data from a list.
Also, search the Web for FusionCharts for SharePoint. You should find a tool that does just that (it was released recently).