This seems to be the biggest stumbling-block... Last standing desks I saw in a store selling office furniture were over $1000. I can't justify that at home, and I doubt that my employer would justify that at work.
I picked up this one on Woot for $300:
It works reasonably well. It's got a hand crank and cranking it up and down is so tedious that I generally just leave it in the standing position, which is probably a good thing since that encourages me to stand more (though could be a bad thing if I left it in the down position). It's more stable than the $1000 electric desk I have at work, typing doesn't make the monitor move around at all like it does at work.