A lot depends on the state you live in, OP.
If you live in a deep red state, your best bet is to do what you can to change hearts and minds where you live, but mostly to contribute to states where the fight is a bit more "live" or to the continuing and future legal battles at the federal level against state bans in general (It's coming within a few years).
Places like Illinois, New Jersey, Ohio, and a few others have important legislative or ballot initiatives ongoing or coming up in the next couple years or so, so seek out organizations in those states and do what you can to help.
I'm also intrigued by this. In states with voter-approved marriage bans, where the gov and attorney general both agree the bans are unconstitutional and both decline to defend them in court, as happened in California, the ban seems like it would be automatically overturned due to today's precedent, no? Surely there must be, in blue and even purple states, govs and attorney generals who will refuse to defend? I hope some organization is investigating: I'm sure they are.
I'm in Michigan.
Michigan has an important fight coming up actually, which will likely be a tough one, and I'm sure they'd welcome your help.
The organization there is called "Equality Michigan," and they even have a "Take Action" page on their website telling how you can get involved.
Perhaps someone might clarify: My understanding is that if you live in a state that does not allow gay marriage (say, WI), you can go to Minnesota or Iowa and get legally married, return to Wisconsin and will still be considered legally married as far as the federal government is concerned and thus be eligible for all federal marriage rights and benefits. You would not, however, qualify for whatever state benefits Wisconsin might offer married couples. Am I correct on that?
This remains uncertain, r4, but will become an issue that will receive some examination and attention in the coming weeks. Some federal benefits are distributed by the state, and others look to the "state of celebration" for whether or not a marriage is valid, others to "state of residence." This seldom matters or has an effect on straight marriages since their marriages are valid state to state.