LINQ to SQL: Making it N-Tier

You can create your application use LINQ to SQL and make it N-Tier. Go ahead and watch out the MSDN Documents

N-Tier and Remote Applications with LINQ to SQL

LINQ to SQL N-Tier with ASP.NET

LINQ to SQL N-Tier with Web Services

LINQ to SQL with Tightly-Coupled Client-Server Applications

Implementing Business Logic (LINQ to SQL)

Data Retrieval and CUD Operations in N-Tier Applications (LINQ to SQL)