Date.com
http://www.date.com/

Yahoo! Personals
http://personals.yahoo.com/

DatingDirect
http://www.datingdirect.com

eHarmony.com
http://www.eharmony.com/

Udate.com
http://www.udate.com/

Lavalife
http://www.lavalife.com/

FriendFinder
http://friendfinder.com/

DreamMates
http://www.dreammates.com/

Match.com
http://www.match.com/

AmericanSingles
http://www.americansingles.com/

Source: Singles Online Dating
http://www.singles-online-dating.com/