.NET 2.0 BETA2: System.Configuration
Most .NET developers will be familiar with the System.Configuration namespace, and in particular with the ConfigurationSettings.AppSettings class. When using this class in .NET 2.0, however, (even tough it will compile) you will see the warning that this is now obsolete, and been replaced by ConfigurationManager.AppSettings, which also exists in the System.Configuration namespace.
In .NET 1.1 the whole System.Configuration namespace existed in the system assembly, and this is also shipped as is in BETA2. However, when you look for the new ConfigurationManager.AppSettings class, you won't find it in there. To use this new class, you need to add a reference to the System.configuration (nope, that's not a typo) assembly, which contains the new version of this namespace.