A lot of people wanna use Access or Excel Services with Sharepoint 2010. But this is only possible with Sharepoint Server 2010 Enterprise.
Here a short comparison of the different Sharepoint 2010 Versions and which Service Applications are supported.
Seen on www.sharepoint2010.at
Here you find a sample service application, called ParagoServices, built on top of the SharePoint 2010 Shared Service Architecure: http://www.parago.de/2011/09/paragoservices-a-sharepoint-2010-service-application-sample/