A while ago I wrote this (Dutch) article on how to perform LINQ to SQL for your SQL Compact databases, since Visual Studio did not understand this, we had to do it manually, as described in the article just mentioned.

But since the release of .NET Framework 3.5 SP1, and the therein included ADO.NET Entity Framework, it is now possible to generate a model out of a SQL Compact database!

Unfortunately this is not (yet) possible for Smart Device applications (Windows Mobile), but who knows what the future might bring!