I recently published a new article on Creating User Controls by Zaheer Akhtar. Here is the abstract from the article:
There are many controls in Microsoft Visual Studio 2005 that certainly save you lots of development time, but there are always opportunities for you to build your own controls to save even more development time. Many business problems require custom controls to simplify the development solution. Custom controls are typically required to obtain different functionality, new functionality, or the combined functionality of several controls.
I am sure you will enjoy the article!