If you're in Nassau, there's the Mother's Center of SW Nassau that meets in the Baptist Church in E. Rockaway. It has a lot of mainstream Mamas, but there are also quite a few crunchy mamas. It's a great group with a lot of activities, a good preschool program, activities for moms (like yoga, book club, knitting) often while members provide child care in the same building, etc.
There is the Natural Mothering Forum which meets up in suffolk county...they have a yahoo group you could search for. There is also a LI babywearing group that probably has some cross over with these other groups. As far as "eco-friendly" towns, unless you go out East, I think that's harder to find.... There's a farmer's market in RVC but I'm not sure if it's sat or sun morning. I think there's one in Westbury, Amityville I think...there is also more than one organic CSA that deliver weekly veggie shares to various areas.
There is a Long Island thread in "finding your tribe" from long ago. It may be archived now. I don't post often any more so am not sure...What area do you live in so I can direct you to more stuff?