Ohio seems to be one of the best organized places regarding recovering the history of the underground railroad. This site shows a great deal of state wide organization and effort to recover this history.
An important resource is the New York State Heritage New York. It was founded a to celebrate the various sites in New York State that are documented as being part of the Underground Railroad. They make up a New York State Underground Railroad Heritage Trail.
The Oneida County Freedom Trail Commission has an excellent web site with color, designs and pictures. The Commission is a county based organization that seeks to recover and tell the story of the Underground Railroad in Onieda County, and the broader story as well.