White Labeling (Easily Rebranding) Rails Applications

Has anyone figured out the best way to white label a Rails app / allow an app to be easily globally rebranded e. g. via configuration?

Sure, provide a way for admins to upload a CSS file and support subdomains/hostnames to load the correct CSS files. If you need to load different data for each one, simply have a table of supported white label sites/customers and then have a field in each table (indexed) for that customer_id.