I can't recommend varidesk.com or geekdesk.com enough. A varidesk is great if your company already supplies you with a non-standing desk and a geekdesk is excellent if you work from home and get to pick any desk you want. Be sure to get a mat to stand on as well.
Most of my day involves me sitting in front of a computer: Programming and designing during the day and gaming at night.
My department has a ton of people who use standing desks, but I never saw the need.
After reading through this thread and thinking about how much sitting I do on a daily basis, I'm more likely to now to ask my company for a standing desk.
I'm hoping this will make a difference.