We've compiled a list of some related web sites which you might find useful:

Bureau of Transportation Statistics (U.S. Department of Transportation)
Center for Transportation and Research Education (Iowa State University)
Center for Urban Studies (Portland State University)
Directory of Transportation Resources (Princeton University)
Environmental Systems Research Institute, Inc. (ESRI)
Florida Department of Transportation
Institute of Transportation Engineers
Intergraph - GIS
McTrans (University of Florida Transportation Research Center)
NCGIA Annual GIS Bibliographic Series (University of Maine)
PC-TRANS (University of Kansas)
The Urban Analysis Group
Transportation, Research and Education Center (Georgia Institute of Technology)
Transport Research Group (University of Ulster)
Travel Model Improvement Program (TMIP)