Galin Iliev's blog

MS MVP Sahil Malik wrote nice serie of short articles about C# 3.0

a) Demystifying C# 3.0 - Part 1: Implicitly Typed Local Variables "var"
b) Demystifying C# 3.0 - Part 2: Anonymous Types
c) Demystifying C# 3.0 - Part 3: Extension Methods
d) Demystifying C# 3.0 - Part 4: Lambda Expressions
e) Demystifying C# 3.0 - Part 5: Object and Collection Initializers
f)  Demystifying C# 3.0 - Part 6: (LINQ) Query Expression Translation (to C# 3.0)
g) Demystifying C# 3.0 - Part 7: Expression Trees

These topics are very good described. Enjoy