RE: Display Dynamics CRM Data on a SharePoint Site
Hi Lutz,
From a CRM side, you need to use the CRM SDK to retrieve the data, which you can display in your SharePoint page.
You can use the CRM WebServices (Organization.svc for SOAP requests or WEB API for REST requests) to perform CRUD operations on the CRM Data.
Please keep in mind that the trend in CRM is to replace the Organization.svc with the new WEB API endpoint - so maybe it would be worth to consider building your application to use that endpoint so that you don't have to change it, in case you upgrade in the future.
Here is a link to help you get started with the CRM SDK: msdn.microsoft.com/.../gg328027.aspx
From a SharePoint side, unfortunately I don't have much knowledge, therefore I'll let other members to contribute to that part.
Hope this helps!
Radu