Here is a list of (some) SAP SuccessFactors Recruiting Marketing (RMK) instances (or their urls, rather). You will find mostly production instances, but I found and listed some test/staging instances as well. It is not a complete list of all running instances, nor does it aim to be that.
The list does, however, give you over a hundred examples of what you can do with Recruiting Marketing and the Career Site Builder (CSB). Some instances are only using default CSB components, other are highly customized. One of the best examples of how far you can take a custom RMK site is this demo set up by projekt0708.
I have not really sorted the list by any meaningful metric, instances are currently simply added in the order they were found. You can also find a more detailed, always up to date version of the list here.
This list is maintained and published for (market) research purposes only. It is meant to provide you with examples for how to use and for what you can achieve with SAP SuccessFactors Recruiting Marketing.