Back to my National Park Passport Stamps site.

Government Sites:

NPS website
NPS List of parks by classification
Recent additions to the NPS units
NPS complete list of parks in the order that they were formed

Collector Sites:

National Parks Cancellation Stamp Group - Message board, chat, lifetime achievement awards, and many posts of stamps

The regularly updated spreadsheet (Master List) of all stamping locations can be found at

Eastern National: List of Stamps that they have given out
Home of the annual Passport Stamp convention
PassportStamps: Similar site to this one
eParks' Discussion Board NPS Passport Cancellation Guide (not really updated)
Daniel Cohen's stamps (not really updated)
New England Information