Update:
Oracle now fully supports the Entity Framework.
Oracle Data Provider for .NET Release 11.2.0.3 (ODAC 11.2)
Release Notes:
http://docs.oracle.com/cd/E20434_01/doc/win.112/e23174/whatsnew.htm#BGGJIEIC
More documentation on Linq to Entities and ADO.NET Entity Framework:
http://docs.oracle.com/cd/E20434_01/doc/win.112/e23174/featLINQ.htm#CJACEDJG
Note: ODP.NET also supports Entity SQL.