Same-Sex Marriage:
 
Alliance for Marriage www.allianceformarriage.org
AFM is spearheading the constitutional amendment that would define marriage as being between a man and a woman. Their motto is "More Children Raised in a Home with a Mother and Father." 
 

BreakPoint www.pfm.org
Charles Colson's commentaries on faith and contemporary culture will help you understand the implications of accepting same-sex marriages. BreakPoint offers a "Speak the Truth in Love Resource Kit."
 

Focus on the Family www.family.org
The ministry of Dr. James Dobson, this organization addresses the issues of family and society in a biblical manner. Their ministry, Love Won Out, offers regional conferences around the country on the subject of homosexuailty.

 
Family Research Council www.frc.org
FRC is primarily an advocacy group that monitors developments in Washington and nationwide. They have been active in the marriage debates
 

Institute for Marriage and Public Policy www.marriagedebate.com
The website provides numerous links, updates and perspectives on the significance of marriage in general and the current same-sex marriage controversies.