Progress Telerik UI for WinForms
RibbonForm is a specialized form that is pre-configured with a RadRibbonBar so that you don't have to spend time setting up this first layer of the UI. It also comes with a set of minimize, maximize and close form buttons so that you do not have to add these yourself.
RibbonForm comes with transparency support under Windows Vista and Windows 7, which can be turned on/off with a single property. It also offers full Theme support which can be used from the very start of your project. You can use any of the pre-defined themes, or build a new one from scratch to fit your exact scenario.