Anytime I think of sleeping at the office I can't help but remember the episode of Seinfeld where George has a carpenter make the underside of his desk roomier and installs a shelf. If you don't have to be so conspicuous with your sleeping habits at the office you may want to look towards the Nappak, the inflatable sleeping quarters. While it's rolled up when not in use, the Nappak takes up very little room, but inflate this unit up and expect it to take up a big chunk of your office, or your entire cubicle.
The large nature of this and the fact it includes wheels when rolled up is definitely peculiar. Expect to have a slumber party in this thing, rolling it from cube to cube? Well, I guess that would work if you have a really relaxed office environment.