This tutorial explains C# and LINQ performance tips with the following topics:
1) String Vs StrinBuilder ,string.format
2) ArrayList vs List
3) List vs Dictionary
4) How to write optimized code in C#.
5) Garbage collector generations 0,1,2.

Tiw webcast shows some exciting new features that turn LINQPad into an essential tool for writing and performance-tuning Entity Framework queries.

Developers discover a lot of behavior in the ADO.NET Entity Framework that is quite unexpected. Programming Entity Framework author, Julie Lerman, will help you avoid some surprises and show you tricks to make the most of Entity Framework. Learn how to provide default navigation property (foreign key) values, practical uses for Entity SQL, how to improve the performance of your LINQ and Entity SQL queries, combine Entities with .NET Generics to write reusable code and more.

Eric Nelson explains what are ORM, EDM, and ESQL, what is the difference between LINQ to SQL and LINQ to Entities, which one is going to be further developed by Microsoft in the future, accompanied by hands on demos showing how to use them.
http://www.infoq.com/presentations/ORM-LINQ-Entity-Framework-Eric-Nelson

Paul Batum shows how you can use Linq to handle Events in windows applications.