On the federal Defense of Marriage Act: the law barring the federal government from recognizing same-sex marriages legalized by the states, was ruled unconstitutional, by a 5-4 vote. The law, which was signed by Bill Clinton in 1996, prevented couples’ marriages from being recognized federally, even if their home state allowed it. Now, if you get legally married in one state, you are granted all federal benefits of marriage. This doesn’t make marriage equality the law of every state, but a full third of the US population lives in a state where same-sex marriage is legal.
On Prop 8: the California constitutional amendment that barred same-sex marriage, the Supreme Court ruled that the private sponsors of the bill didn’t have legal standing to appeal the decision of a federal judge who struck it down. It doesn’t really speak to the topic marriage equality, it’s merely a procedural decision. But it does have the effect of paving the way for same-sex marriages to resume in California as soon as next month.
You can see how this affects each state here.
Another SCOTUS ruling, on workplace harassment, was also rendered: it makes it harder to fight back against abusive bosses or coworkers if they can not technically fire the complainant. Companies cannot be held liable for harassment that happens on their watch unless the harasser has hire/fire power. Without legal liability, companies have far less incentive to stop harassment or take complaints seriously.