Local Organizations:

Green Plan Philadelphia http://www.greenplanphiladelphia.com/

NeighborhoodsNow http://www.neighborhoodsnowphila.org/

Fels Institute of Government http://www.fels.upenn.edu/civic-exchange/

Philadelphia City Planning Commission (www.philaplanning.org)
Delaware Valley Regional Planning Commission (www.dvrpc.org)
City of Philadelphia (www.phila.gov)
Center City District (www.centercityphila.org)
10,000 Friends of Pennsylvania (http://www.10000friends.org/)
American Institute of Architects Philadelphia (www.aiaphila.org)
Delaware River Port Authority (www.drpa.org)
Fairmount Park Commission (http://www.fairmountpark.org/)
Pennsylvania Horticultural Society (http://www.pennsylvaniahorticulturalsociety.org/home/index.html)
Southeastern Pennsylvania Transportation Authority (www.septa.org)
East of Broad Improvement Association
http://www.ebaphila.org/homepage.htm

Planning News
National and worldwide
Planetizen (www.planetizen.com)
American Planning Association (www.planning.org)
Cyburbia (www.cyburbia.org)
The Next American City (www.americancity.org)
Local
Philly Skyline (www.phillyskyline.com)
Changing Skyline (www.changingskyline.blogspot.com)
Design Advocacy Group (www.designadvocacy.org)

Data Resources
Local
Philadelphia Zoning Code (http://municipalcodes.lexisnexis.com/codes/philadelphia/)
Philadelphia CityMaps (http://citymaps.phila.gov)
Pennsylvania Spatial Data Access (www.pasda.psu.edu)
National and worldwide
American Planning Association (www.planning.org)
Brookings Institution Center on Urban and Metropolitan Policy (http://www.brook.edu/)
Congress for the New Urbanism (http://www.cnu.org/)
Urban Land Institute (www.uli.org)
U.S. Census Bureau (www.census.gov)
U.S. Department of Housing and Urban Development (www.hud.gov)
HUD User (www.huduser.org)
The Urban Institute (www.urban.org)
National Trust for Historic Preservation (www.nationaltrust.org)
Lincoln Institute of Land Policy (http://www.lincolninst.edu/index-high.asp)
National Housing Institute (www.nhi.org)
Google Earth (http://earth.google.com/)
Windows Live Local (http://local.live.com/)
http://www.cml.upenn.edu/nis/