Which open source job skill is most in demand?

It's no secret that open source skills are in hot demand. Whether you're a developer writing the code that will run tomorrow's websites or next hot application, or a system administrator who is helping keep a company's IT infrastructure up and running, chances are you work with open source software along the way.

But which skill set is in the hottest demand? We turn to you, our readers, to let us know what you're seeing out there in the job market. Does demand match the skills you find on your resume, or are you seeking to enhance your background in a new area to make a job transition?

Whatever the case may be, weigh in and let us know, and tell us what skills you are seeing in the most demand in the comments below.