We published a step-by-step tutorial about Transparent Controls. There are many screenshots, and you can download the sample code as well. Hope it helps!
RegionControl is a universal and powerful control for creating attractive GUI for .NET Compact Framework. It allows the developer to design various kinds of menus, buttons, toolbars, buttonbars which all may have arbitrary shapes and appearance. Get a free evaluation version here and see it yourself!
bee Mobile has released another control which aim is to help developers to create cool and attractive Windows Mobile applications - WaitingBar. It is a visual indicator informing the user of a background task being performed. With its charming laser-like appearance it gives applications professional modern look. More information can be found here.