Mike Taulty has a really nice overview video here.  I have spent much more time looking at LINQ to SQL than LINQ to Entities (which is just using LINQ queries against the ADO.NET Entity Framework).  I plan on digging in to the ADO.NET Entity Framework soon (it's on my laundry list of TODO's!).  Remember, LINQ to SQL is only for SQL Server.  LINQ to Entities / ADO.NET Entity Framework will work against other databases (using db specific providers).

-Marc