User proximity search?
There are two basic approaches for doing locations in D7:


the location and gmap modules
the addressfield, geocoder, and openlayers modules


According to Karen Stevenson's presentation at Do It With Drupal 2011, only location/gmap currently has location proximity search working in D7... but not very well.

Based on this presentation and the book Mapping with Drupal, I set up proximity search on my own site using the location module.  It works, but it's not terribly user friendly, it's a pain to theme, and it's still clearly under development.  However, it's a far better solution than I would have been able to arrive at rolling my own.