When .NET 3.5 is released later this year, it will include several changes to the "red bits" including new types and methods. Scott Hanselman has posted a list of new types and methods with links to the MSDN documentation.
The so-called "red bits" are any libraries that existed in .NET 2.0 or 3.0. As .NET 3.5 is not supposed to be a major release of the .NET framework, changes to red bits were supposed to be minimal. This is in contract to the "green bits" which consist solely of new libraries.
Several of the new methods are in support of the new class DateTimeOffset. This is a date/time type with support for time zone information. This replaces the DateTime class for many scenarios.
New enumerations for the garbage collector suggest that developers are going to be getting more control over how the garbage collector functions. This is a break with earlier .NET designs which, unlike Java, pretty much expect the developer to not need to tune the GC.