LINQ is one of the newest, and most exciting (IMHO), features in the .NET Framework 3.5 (Visual Studio 2008).  In short, it's a feature that allows you to treat Objects, SQL Data Sources, XML, etc. with the same Query Language (SQL-Like).  For example, one of the things that I as a developer hate having to do, is work with the XML Objects in order to transverse/lookup XML Data from an XML file.  Typically, if the file is small enough, I will convert it to a DataSet and then use SQL Queries to manipulate/Search the file.  The big problem there is that there is a major overhead if the file is large, or if I only need the data for brief periods of time (i.e., constructing and tearing-down the ADO.NET Dataset structure).  With LINQ, I can access the XML DOM with SQL-Like statements without having to load the whole thing in memory like a Dataset, no matter what the size of the file is.  Anyway, that's one of the reasons that I think that LINQ is a very nice new feature.

Here's the description of the HOL:

These Visual Basic LINQ Hands-on Labs provide an introduction to the LINQ Project. Learn basic LINQ features, including the Standard Query Operators, and see how these features can be used against in-memory collections, connected databases, and XML documents. The labs also provide a clear picture of the relational data access support provided by the LINQ Project, referred to as LINQ to SQL.
The language integrated query framework for .NET (codenamed “LINQ”) is a set of language extensions to C# and Visual Basic and a unified programming model that extends the .NET Framework to offer integrated querying for objects, databases and XML.

Here's the download for the labs: (Click here)

~ Robert Shelton