The only real/ergonomic solutions are these:

http://www.ergotron.com/portals/0/html/exploreWorkFitAll/mat...

I use the WorkFit-C for about 10 years now and I can tell you: With this one, the standing desk discussion is over!

I use an Ergotron monitor arm to move my monitor between sitting and sanding positions. When I stand, I put my keyboard and mouse on a small shelf. There's really no need to move the whole work surface up and down.