Can you use Microsoft Entity Framework with Oracle?

DevArt's OraDirect provider now supports entity framework. See http://devart.com/news/2008/directs475.html

Yes. See this step by step tutorial of Entity Framework, LINQ, and Model-First for the Oracle database (11G), and using Visual Studio 2010 with .NET 4.

Oracle have announced a "statement of direction" for ODP.net and the Entity Framework:

In summary, ODP.Net beta around the end of 2010, production sometime in 2011.

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.