Just completed a new documentation page to help developers get going quickly with mojoPortal.
Hello World - Developer Quick Start
The article has a zip with sample code you can drop in and start hacking on with a few simple steps as indicated in the article. It shows how you can use a plain old UserControl or a UserControl that inherits from SiteModuleControl. Both examples also illustrate the use of the ASP.NET UpdatePanel for ajax postbacks.
Enjoy!