We all know that we sit down too much during the day.  This is true of teachers, people who work in the Internet sphere, etc, and etc.  How can we avoid this you might ask?  Well how about a cheap-as-chips standing desk that can be found at Target.  Find yourself a solid wooden table, I chose red but there are multiple bright colors (as well as "natural") and a stack-able shoe rack.  Add some duck tape and BOOM, a standing desk that is ergonomic (lifts the screen as to be eye level) and completely transferable. 

Of course, the desk itself isn't free but most businesses, wherever you work, will provide you with some kind of basic desk.  The only thing that you need to keep in check is how high the first shelf needs to be in order for you to stand tall and have your arms be nearly 90 degrees.  If you are clueless on why you need a stand up desk then you need to read this piece by Graham Peterson (or someone in the company).  If Target isn't near you then may I recommend IKEA due to most of their stuff being incredibly hackable.