<p>Answers to a recent post (Any chances to imitate times() Ruby method in C#?) use the <b>=></b> operator in the usage examples.  What does this operator do?  I can't locate it in my C# book, and it is hard to search for symbols like this online.  (I couldn't find it.)</p>

It's not really an operator as such, it's part of the syntax for lambda expressions. In particular => is the bit which separates the parameters from the body of the lambda expression.
Does your book cover C# 3.0? If not, it won't include lambda expressions. If it does, it should really cover them! Hopefully with the right terminology, you'll be able to find it in the TOC or index.
EDIT: A bit more information: A lambda expression is a piece of syntactic sugar to either create an instance of a delegate
or
an expression tree (the latter being new to .NET 3.5). Lambda expressions almost entirely replace anonymous methods (from C# 2.0) although they don't support the notion of "I don't care about the parameters" in the way that anonymous methods do.