Cleaning a PC

I work in a manufacturing environment and the computer back in the shipping office is constantly getting dirty due to people opening the door, etc. We blow it out regularly, but it is really dirty. What is the best way to clean some of the caked on dirt off the components such as the memory stick? And, I know you can get plastic cases or something to put them in to aleviate some of this, anyone know where to find them? Custom would be too expensive. Thanks!