Yesterday, during the TechDays in Geneva, I met quite a lot of people asking about the availability of LINQ to SQL providers for databases other than SQL Server.
Unluckily, at least from Microsoft side, nothing has been announced yet (third parties neither) and I don’t think it will happens.
On the other side speaking of LINQ to Entities and therefore from the Entity Framework things are quite different. In fact for the Entity Framework that will ship in second half of 2008 with SQL Server 2008, third parties have already planned to build providers for this LINQ flavor for a variety of database. If you want to have a list of the planned LINQ to Entities providers have a look at the following press release: http://www.microsoft.com/presspass/press/2007/dec07/12-06EntityBeta3PR.mspx