1. SOCIAL MEDIA, CMS, HTML, CSS & ALL THINGS DIGITAL
As an editor, you are responsible for the content for your brand, not just the ink-on-paper version of it. You will be asked to blog, tweet and write for the web. If you don't know how (or if you do it badly), you will get left behind. Bonus: advanced knowledge in the digital arena makes you a candidate for web editing jobs – practically the only area of magazines that is growing right now.
2. PHOTOGRAPHY
That blog you're writing? If you can do the photography for it, you're worth more. More photos make for better blogs, especially when there's variety other than just product shots supplied by PR people and the quality is better than a basic snapshot. (Yes, I acknowledge the fact that I rarely post photos on this blog.)
3. GRAPHIC DESIGN
Know photoshop? Now you can resize and edit those photos for your blog without bugging the art department. Understanding the basics of design will also help you better communicate with the art department (just remember: they still know more than you – respect their expertise). Plus, being able to think visually and explain it will help you develop and execute editorial packaging concepts, which depend on a successful marriage of text and images/layout.4. COMPUTERS & ELECTRONICS
If you can troubleshoot email problems and get the AV equipment running at a meeting, you portray an overall air of capability. Plus, you don't have to bug IT as often. (But again, respect their expertise.)
5. PUBLIC SPEAKING
Editors are brand ambassadors and one of the more powerful tools in a magazine's marketing arsenal. Excel at making presentations (at a consumer show, for example) or doing demonstrations (for that web video, say) and you may find yourself one of the public faces for your magazine.
6. SPECIALIZATION
You do risk pigeonholing yourself, but being an expert in a particular area, for example beauty or environment, will make you a top candidate for positions requiring knowledge of that subject.
Any other skills you would add to this list?