Californians Against Hate (CAH) is a group dedicated to "out" those who contribute money to the cause of denying same sex marriage rights. CAH recently published their "Dishonor Roll," a list of individuals, companies, and organizations who donated big dollars ($5000 or more) in the effort to help pass Proposition 8. Check out the list, Californians in particular. Boycott where applicable; shake your head in disapproval where your consumer power isn't.
Here's an example, according to CAH,
"San Diego businessman Terry Caster, who owns A-1 Self Storage Company was California’s 2nd biggest individual contributor to the Yes on 8 campaign. Caster and his family gave nearly $700,000 to Yes on 8, including $400,000 just five days before the election."