STL/CLR - a fairly low key, but awesome new addition in .NET 3.5
I really like what the C++ team have done here, they've essentially created a subset of the stuff found in the C++ STL but included error checking and stuff like that - of course this all requires .NET 3.5.
It seems that the STL/CLR stuff has been a victim of the more cooler features in the app languages C# and VB.NET like LINQ, and err... LINQ.
Check it out here - http://msdn2.microsoft.com/en-us/library/bb385954(VS.90).aspx.
I believe that all the containers act like their C++ STL counterparts from an interaction perspective, with a few under the hood error checking things thrown in to make them "safer". I mean where would you be without the trusty vector container?! :-)