Hi,
Feature instances can be arranged in left center or right panels but cannot render side by side within the same panel.
Rather than using multiple html content instances (each of which makes their own hits to the database), you can do layout all within a single content instance (and get better performance). See the included content template examples that show how to do column layout within a single html instance.
Note also that the home page of this site which appears to have 3 columns and then more content below it is really just one html content instance with floated columns in the content itself.
Hope that helps,
Joe