I get the bug to go on this quest.  It looks fairly doable.  I download the file of stamp locations from Eastern National http://www.eparks.com/eparks/cancels.pdf.  I also order the passport book from them.  Using the file and the NPS web site – especially the state map National Park Guide Map, I start to plan several trips on Microsoft Streets and Trips (I currently am using the 2002 version).  I eventually settle on an initial plan of 6 trips, all starting and ending in Sylmar, CA (just north of Los Angeles).