I bought a small aloe plant for my office and it came in a small pot (around 8cm). I've only seen the aloes that get quite large, but I would like to keep this guy small since it's just sitting on my desk. Will it get out of control unless I keep an eye on it or is this just a different kind of plant than the larger variety?
If it is a true aloe vera, then it will eventually need a larger pot, because it will create "pups" (small offshoots) around its base, which will then grow to full size (maybe as tall as 18") and then produce pups of their own, which will then grow to full size...
The smallest pot I'd try to keep a true aloe vera plant in would be a 12" (30 cm) pot. And even in that size pot you will need to divide it now and then in order to keep it healthy, because when they are happy they can grow pretty quickly to fill that space. Dividing will give you new plants to keep or give away. Rooting new plants is pretty easy. Basically, you pull off side shoots, and stick the stems into a free draining, sandy soil, and water very sparingly until you see new growth.