Lots of fun :) Reminds me of the time at a previous job when I had to incorporate distance measurement based on post codes (zipcodes, UK style). There wasn't a whole lot to do for long periods at this job (which is why I left it eventually) so I spent several days making pretty pictures from the postcode data. I was quite amused that the density of codes in London was such that I could see the Thames winding through the middle :)
I also spent a while trying to guess polygon data for the post districts from just the point data for each code. I found that quite hard at the time.