Anyway, I've uploaded an article (PDF document) that attempts to give the reader a brief introduction to shift registers. Theory is all well and good so there are some simple construction details for a PIC based project that can control up to 255 x seven-segment displays. All the source code and diagrams etc are supplied so the constructor can change the firmware to fit their own requirements.
UPDATE 20th Sept, 2013.... Just uploaded the correct version of the PDF file... sorry about that.