I got a question about PSAP today and thought it would be worthwhile to post to the CTPP listserv:

To be short and sweet, PSAP is largely for TRACT and BLOCK GROUP definition for the 2010 Census.  http://www.census.gov/geo/www/psap2010/psap2010_main.html   There are probably other geographic areas that are also included. 

From glancing through the PSAP materials, it appears that the Census Bureau wants you to contact their regional office:

http://www.census.gov/field/www/

However, you may want to contact your State Data Center (SDC) who may already have established lead agencies for different counties in your state.  http://www.census.gov/sdc/www/

Elaine