I printed out the Punnet case earlier today and found that it didn't quite fit my brand new Pi, which was delivered earlier this week. Since I have seen a lot of case designs that are awaiting measurements of a real Pi, I decided to take out my ruler and produce this version of a printable case. Although I produced the diagrams from scratch, it is very similar to the Punnet, so if you want instructions for assembling it, please look there (my industriousness only extends so far...).
It fits my Pi quite snugly. Depending on the manufacturing tolerances, it may or may not fit yours.
I have included the original Visio diagram and a PDF version. NOTE: Please select the 'Actual Size' option when printing the PDF. By default the 'Fit to Page' option is checked, which messes up the measurements.
Download it here: