I recently built a site for finding vineyards, and used GeoDjango with Postgres+PostGIS.

Setting up was a small PITA, but a bounding box query looks like this:

  footprint = Polygon(((ullon, ullat), (lrlon, ullat), (lrlon, lrlat), (ullon, lrlat), (ullon, ullat)))
  vineyards = Winery.objects.filter(loc__within=footprint)

If you're interested, check it out: http://finelocalwine.com/