I have a script that it commented through out, that can do these calculations. I have both the U.S and Canada data sets. The U.S. data I just updated on February 5, 2006. The Canadian data I last updated on Jan 15, 2006. They both contain every postal code and city info, including populations that is valid from Dec 2005. The data sets use Geo Plate formula, which allows for very close to near driving distances and flying distances using the routing tables which commercial airlines must follow. All of this is done using just MySQL, without the need for a high end GIS data set.
It includes the data set (dump), scripts/classes ( distance, sql), templates (2 sets), (2) PSD pre-sliced so you can change the colors and text. The U.S. script contains 3 examples...
distance by zip code
radius by zip code
closest Post Office from a (physical address, 12 Beacon St, Boston MA) post office data has, phone, fax, hours of operation, dates closed
Canadian contains 3 examples
distance by zip code
radius by zip code
distance city, province
If you want the Canadian set PM and I will give you a link to it. You can also get the U.S. set, PM for that link.
I don't have the Canadian example up but I will put it tomorrow so you can try it! I 'll also put the post office one up tomorrow as I just looked and I don't have that data set at home with me!
U.S.
Zip Code Example
http://www.lovemedammit.com/distance/zip.php
Radius Example
http://www.lovemedammit.com/distance/radius.php
If anything, the examples will each you how to do better calculations than lame point to point measurements!
yj!