There's been a lot of excitement about a new language feature in the .NET Framework 3.5 "Orcas": extension methods.
Extension methods allow developers to add new methods to the public contract of an existing CLR type, without having to sub-class it or recompile the original type. -- ScottGu's Blog
That's High Geek for "you can tack on methods to existing .NET classes." For example, you could extend the String class with a UrlEncode method:
C# Extension Method: UrlEncode
public static string UrlEncode(this string s)
Then you could call it from any string:
string str = "blah";
string strEncoded = str.UrlEncode();
String.prototype.UrlEncode = function()
So, as far as the coming extension methods in .NET go, I guess I'm less "wow, neato" and more "it's about time." I'm *such* a jerk.