BEST place to start

http://ourpublicservice.org/OPS/

Political Jobs/Lobbying Firms/Government Contractors

http://www.hillzoo.com/
http://www.cq.com
http://www.rcjobs.com

Government Jobs and Internships

http://www.careersingovernment.com/
http://www.whitehouse.gov/government/independent-agencies.html
http://www.whitehouse.gov/government/wh-intern.html
http://www.loc.gov/rr/news/fedgov.html
http://media.newjobs.com/opm/www/usajobs/pdf/ei-25612.pdf
http://www.usajobs.gov/
http://federaljobs.net/oscholar.htm

Other Government Opportunities

http://www.careers.state.gov/civil-service/index.html
http://www.careers.state.gov/officer/index.html
http://cpol.army.mil/
http://www.defenselink.mil/sites/c.html#civjobs
http://www.cia.gov/employment/index.html
http://godefense.cpms.osd.mil/
http://www.nsa.gov/careers/

Non-Governmental Organizations

http://pvo.usaid.gov/usaid/
http://guides.library.duke.edu/ngo_guide
http://www.un.org/wcm/content/site/dpingorelations/
http://www.idealist.org
http://www.interaction.org
http://www.oneworld.org

Government Contractors Examples

http://www.boozallen.com
http://www.kadix.com
http://www.sra.com/

State and Local Government

http://www.statejobs.com/gov.html
http://www.virginia.gov
http://www.charlottesville.org/Index.aspx?page=91