Around Aug 2008 Microsoft published a sample Entity Framework provider for Oracle which uses the Microsoft OracleClient - which has been deprecated in .Net4.0. As Microsoft folk were nice enough to do half the work for us it was a good time to give this a shot. I've converted the project to use ODP.net 11.1.
The project EFOralceOdpProvider is hosted on Codeplex - of course. So far it has been subject to very little testing. Please do send any feedback and if you would like to contribute to this project please drop me a line and I'll add you to the project.
Update 14/04/2011: In Feb 2011 Oracle finally release a beta version of their official Entity Framework Provider. Download is available here http://www.oracle.com/technetwork/topics/dotnet/downloads/oracleefbeta-302521.html