UPDATE: My answer now supports automated change of the product base image after swatch. You can also find a more detailed tutorial on how to do this including more images here.
Magento CE 126.96.36.199 comes with a very nice new feature: Configurable Swatches. Unfortunately, this is only available for the RWD package, that comes with the default Magento installation. This is a self answered question on how to make the Magento Configurable Swatches available for the Default package. For anyone who wants to integrate the Configurable Swatches into a custom theme, this info may come in handy as well.
Note 1: This is meant to be an introductional guide on how to make the Configurable Swatches available for Magento's Default package. This could (but may not) work for every custom theme. Always backup your original files (and database) before making any changes.
Note 2: The swatches do work (screen shot below), but I did not yet get the product image to change automatically along with the swatches. I will try and look into this when I find some time.
Feel free to contribute by commenting and make suggestions!