If you're absolutely certain you're going to run only text-based word processors or spreadsheets on an IBM-compatible, or simple word processors and spreadsheets on a Mac, you can settle for a basicbox with one megabyte of memory and a 40-megabyte hard drive.
The second place winner at the Husky Startup Challenge, genius.box, takes that basic concept but replaces the Fruit of the Looms with simple to perform science experiments.