It really depends on what you want to do. Do you want to specialize or be a generalist with deep knowledge in several areas? Do you want to focus on internal system administration or Internet-facing system administration? Do you care for administration or architecting of systems?
If you want to pursue a well-rounded education aimed at web hosting, for example, I would recommend pursuing MySQL/Oracle expertise, a web-oriented programming language forte (PHP, ruby, Java -- has actual certification track, etc.), Cisco certification track, and security certification.
Nothing, however, beats doing the work and having a proven, demonstratable skill set. However, your question is about employer-sponsored certification tracks, specifically, and not marketability. I assume you will put in use what you learn and are certified in -- that will make it worthwhile to your employer and to YOU! Which brings us back to my first paragraph: it really depends on what you want to do.