I work at an Ergotron Workfit-S: http://www.ergotron.com/tabid/640/Default.aspx it's a contraption you drop on top of a regular desk, and provides a keyboard shelf as well as mounting for monitor(s) and laptops (I am now on a dual monitor, previously had 1 monitor + laptop shelf, so I'd drop my mbp on it and connect to the monitor). The whole thing slides up and down, and the shelf moves independently as well. Lets me move from sitting to standing easily, lets me adjust to different postures and moods etc.

Been using one for over a year now, very happy with it.