Some of our interests intersect, Art. (Green housing, public transit) I've switched a couple of times, each for the better re my own satisfaction - from immunology research tech to studying for four more years (night classes) at the same time as working full time in landscape architecture, to being a project manager at an interesting land arch firm, to having my own firm(s), one with an art gallery (I'm also a painter, but that's not a change). I have financial problems, but those are mostly unrelated to the career choices.
Somewhere in the middle of that, probably in one of the heavy recessions, and when I was most driven-interested in land use issues, I considered working at a local think tank. A friend with a doctorate straightened me out, as in "no, honey, you need a PhD". Whether or not that was true, I had further qualms about that particular tank, and just kept on keeping on.
Jespah's advice seems right on. I'd also look into conferences being held re your interest area.
Some old a2k land use threads - not all re green buildings/transportation.
I know I started a lot of threads about small houses/prefabs but forget whatever tags I gave them.
http://able2know.org/tag/land_use/
A link you might look at, that covers a lot of architecture, but also covers a lot of eco issues:
http://www.archnewsnow.com/
The newsletter comes near every day; I often skip over it, or delete without looking, but sometimes I learn a lot. Perhaps you'll learn of firms doing interesting work.