This group looks good: Citizens Climate Lobby, "Political will for a livable world." And I do like their "Ask Me How to Make $1,500 and Get Clean Air" tagline, which needs to be a bumper sticker.
"The fundamental problem of climate policy is on the political leadership and corporate power side", Rick Piltz of Climate Science Watch points out; so it's more effective to focus energy there, both on the "political will for climate action" part, and on the "reform politics to make it work better" part.
(Or at least that's my perspective du jour; stay tuned.)
(The other consideration is, what if you speak like Paul Graham but don't write like Paul Graham? How do you weigh your strengths and preferences against the biggest needs in the "move America forward" ecosystem?)