Windows Workflow Activities
A very good MSDN Mag article on the activities that are available OOTB in WinWF.
Activities are the building blocks of workflows. You create workflow solutions by composing activities in the Visual Studio 2005 designer. Like server controls in ASP.NET and controls in Windows Forms, workflow activities are the essence of the solution and form the primary tool chest for developers. The Windows Workflow Foundation provides a number of in-box activities to cover the most common needs. Here I reviewed the native activities that cover transactions, parallel and conditional execution, loops, and exception handling.