Blogger Justin Palmer moved to Portland, OR after a childhood spent in rural Tennessee because of the access and availability that the city offered. But with a new member of his family and a different set of priorities in housing requirements, he found himself with a challenge: finding a reasonable house that adhered to a simple set of requirements.
The two requirements he was filtering for in addition to being in a more spacious part of town was foot access to grocery shopping and quick access to a rail line.
Palmer was able to use a toolset including GDAL and PostGIS as well as styling tool Tilemill. The original post provides a solid and interesting walk through of his process.