Linq to SQL is said to be out of date. You should use the Entity Framework instead as this will continue to be developed and supported by Microsoft.
Theres not much difference between the two though.
Edit
re. references it was in a podcast interview with some of the EF guys. Might have been this one (Im not totally sure I listen to a lot...)
The basic summary as I understand it :
Linq to Sql was developed by the C# team. The main reason it was developed was to demonstrate the power of Linq. Now the team have more important things to worry about than improving database access (like the whole of c# land) so they aren't really focussing on developing it further.
Entity Framework was developed by the ADO.net team. They are all about database access and are spending all their time working on taking EF forwards.
So it's not so much that Microsoft are dropping support for Linq to SQl, but that they aren't doing anything more with it, whereas EF is and will for the foreseeable future still be actively developed. So the general advice is if you are using Linq to SQL continue using it, but if you are starting something new - you should choose Entity Framework.