This post at Lifehack about stand-up desks caught my eye. I've found myself working this way at home recently -- we have a jelly cupboard in our library that's about the perfect height for me, and since it's in the middle of our first-floor is the perfect place to check e-mail or work on a project and still keep an eye on the kids.
I've also found it to be more comfortable than sitting because a) after a day of sitting I'm ready to stand for a while and b) chasing and lifting a 1-year-old is hell on the back. It's a barebones setup that's nothing like the desk that Lifehack found -- just a laptop, a mouse and a power cord -- but it's been working for me.