How to include 3rd party charts in Reportservice 2005

Can someone help me how to include 3rd party/cystom charts in Reportservice 2005? (=non std charts!)

If the third-party chart is not designed for RS (it is not designed as a custom report item), you won't be able to use that control. If by a custom chart you mean your own chart control, you can convert it to a custom report item as shown here, and use it on your reports.