Australia - http://www.austemb.org/ - public.affairs@austemb.org
Azerbaijan - http://www.azembassy.com/ - azerbaijan@azembassy.com
Bulgaria - http://www.bulgaria-embassy.org/ - office@bulgaria-embassy.org
Colombia - http://www.colombiaemb.org/ - emwas@colombiaemb.org
Czech Republic - http://www.mzv.cz/washington/ - amb_washington@embassy.mzv.cz
Denmark - http://www.denmarkemb.org/ - wasamb@um.dk
El Salvador - http://www.elsalvador.org/ - correo@elsalvador.org
Estonia - http://www.estemb.org/ - info@estemb.org
Ethiopia - http://www.ethiopianembassy.org/index.shtml - http://www.ethiopianembassy.org/faqs/index.shtml
Georgia - http://www.georgiaemb.org/Home.asp - embassy@georgiaemb.org
Hungary - http://www.hungaryemb.org/ - office@huembwas.org
Italy - http://www.italyemb.org/ - affariconsolari@itwash.org
Japan - http://www.us.emb-japan.go.jp/ - No Email?
South Korea - http://www.koreaembassyusa.org/ - political_usa@mofat.go.kr; consular_usa@mofat.go.kr
Latvia - http://www.latvia-usa.org/ - Embassy@Latvia-USA.org
Lithuania - http://www.ltembassyus.org/ - info@ltembassyus.org
Macedonia - http://www3.sympatico.ca/emb.macedonia.ottawa/ - emb.macedonia.ottawa@sympatico.com
Netherlands - http://www.netherlands-embassy.org/ - No Email?
Nicaragua - http://www.un.int/nicaragua/ - No Email?
Philippines - http://www.philippineembassy-usa.org/ - info@philippineembassy-usa.org
Poland - http://www.polandembassy.org/ - No Email?
Romania - http://www.roembus.org/ - Ambassador@roembus.org
Slovakia - http://www.slovakembassy-us.org/ - info@slovakembassy-us.org
Spain - http://www.spainemb.org/ingles/indexing.htm - Online Form
Turkey - http://www.turkishembassy.org/start.html - info@turkey.org
United Kingdom - http://www.britainusa.com/ - public.enquiries@newyork.mail.fco.gov.uk
Uzbekistan - http://www.uzbekistan.org/ - uzbconsul_dc@yahoo.com

Afghanistan, Albania, and Eritrea don't seem to have an online diplomatic presence, but the latter two might have some appropriate governmental sites.