Geocoding and Distancing and Latitude and Longitude and umm Stuff

Okay this is complicated stuff. Working on putting together a new site for a client, I have a table of locations with longitude and latitude fields for every row (I actually had a tab delimited file, but I sucked it into the db). For the functionality on the web front end a user needs to search by distance, e.g. find all locations within 10 miles of a zip code. Um okay, so how the hell do I do this?
Well first of I need to get the latitude and longitude for a zip code. For that I very quickly found…