LINQ (from a Java Programmer's perspective) is a shot at an ORM package that is integrated with the runtime - so no additional packages needed. So that's neat...
But wait, there's more - it also provides a querying syntax / structure that's abstract enough to even be used on standard collections, like arrays, lists, etc.... now that's cool - and it can eliminate a bunch of code when doing simple things like looking for a "User" object with a last name of Smith in a List.....
But one of the coolest features of this thing - is that it is built on all the other neat things that have been released with this environment (see: delegates, lamdas, dynamically typed variables [var], among some other things).... why is this neat - cause if you jump into the LINQ rabbit hole - you will learn a number of other things along the way.....
Here is a GREAT LINQ, er, link.... enjoy:
http://en.wikipedia.org/wiki/Language_Integrated_Query