Check out the following blog post from Marco Amoedo for a list of new CRM 5 features.
http://marcoamoedo.com/blog/summary-of-xrm-and-crm-5-at-pdc09/
- Solution Packaging
- Net 4.0 Support out of the box
- Flexible Web Services
- Using System Types
- Linq for CRM
- ADO.Net Data Services and .Net RIA services support
- Code Sandboxing
- Claims based Authentication and Federation
- Shared Picklists