1. Windows Sharepoint Service (WSS 3.0) + Office web part
In the previous version of WSS(v2.0), there is a free Office 2003 Add-in: Web Parts and Components, which is not available for WSS 3.0, however you can still add it manually. It's easy to use and config, but not flexible enough, it also requires the client PC has to have Office 2003/2007 software intsalled to see the graphic.
2. Windows Sharepoint Service (WSS3.0) + Reporting Service web part
You can also use Reporting Services Add-in in WSS 3.0, then create a rdl report and call it via Report Viewer web part. Because it's a rdl report, so it's very flexible .
3. ASP.Net + FusionCharts
FusionCharts is a flash charting component that can be used to render data-driven & animated charts for your web applications and presentations. It does provide a free version. So if you want to build up a flexable(let's say: multi-tenants etc.) dashboard to integrate with CRM, it's a good idea to build up your own ASP.Net page with FusionChart. I would say it won't disappoint you.
4. CRM Analytics Accelerator
This well-known add-ons is not available for CRM 4.0 at the moment, but it coming soon. More details see: CRM Accelerators – Part I – Analytics Accelerator