The Saturn Homebrew Repository for Example Code, or SHREC, strives to provide working examples of code necessary to create homebrew games for the Sega Saturn using tools currently available for free online.
Jo Engine is popular and actively maintained 2D game engine for the Sega Saturn. It can be downloaded here. It has documentation for its libraries and active forums to ask technical questions and share code examples.
For examples using Jo Engine, it would be best to run test code in
\JO Engine\Projects\[YOUR-CODE-FOLDER-NAME], where
\Jo Engine\ is the main directory containing the engine files and tools.
Z-Treme Tools is a set of tools developed by XL2 that build of SGL and Jo Engine.