One example is wordpress sites that can be easily reskinned via wordpress themes. A million wordpress sites running the same backend can look and feel different. Selling themes for wordpress can make cash as well as themes for other systems like Magento. The themes will need to be good and have a lot of features for a premium to be charged.

There are a lot of white label products out there that can be reskinned and marketed as stand alone products. For example DaCast for video streaming. Lot's of affiliate programs allow you to host your own copy of a white label product and brand it as your own product.