The official source of information on Managed Providers, DataSet & Entity Framework from Microsoft
The information in this post is out of date.
Visit msdn.com/data/ef for the latest information on current and past releases of EF.
Oracle recently announced that they’ve released a Beta version of their provider which supports Entity Framework. Features include LINQ to Entities, Model First development, and support for the Entity Data Model Wizard. You can download it here. Oracle previously released a Statement of Direction which discusses their plans and timeframe for a production release.
For a full list of Entity Framework providers, check out this page on the MSDN Data Developer Center.