I read Jan ‘s blog quite often, and last week he came up with this great (free) Webpart (here) to display a graph of any list in your Sharepoint site.
After a few problems I finally got around it so below are the steps to follow.
Silverlight Graph taking data from a Sharepoint list.
run the SETUP.EXE to deploy the Webpart
open (each ) Site collection where to use the WP, and activate the Site Features under site settings
Configuring IIS for Silverlight Applications (following http://learn.iis.net/page.aspx/262/silverlight/)
3a) create a VBS file containing
Const ADS_PROPERTY_UPDATE = 2
if WScript.Arguments.Count 3b) execute
ADDMIMETYPE.VBS .xap application/x-silverlight-app
ADDMIMETYPE.VBS .xaml application/xaml+xml
ADDMIMETYPE.VBS .xbap application/x-ms-xbap