One way would just be to do a google search for 'Ecovillage' and then examine the websites you find. Many of them have websites (although not exactly modern websites) that will have information about what they are, where they are, how to become a member, whether they have interns or places for transients to stay. Many of the bigger and older ones do. Here are a couple of the more well known ones you may have heard of:
Dancing Rabbit is near Rutledge, MO and has a fairly up to date website. They have a lot of internships and the like. I've had many friends take classes or do internships there. Here's what they have to say about learning more about them, from their about page:
If you are interested in Dancing Rabbit, you have lots of options:
subscribe to our blog, arrange a visit, or come do a work exchange
stint. We are actively seeking new members to share our lives and
goals. Together we can build our dreams!
Earthaven is near Black Mountain, NC and also has a fairly up to date website. They also seem to be a place of many internships and classes. I've got some friends who've visited and speak very highly of it. From Earthaven's about page:
We teach workshops on starting an ecovillage, and designing an
ecovillage. See our Calendar for details. For those seeking in-depth
information about ecovillages and intentional communities, we offer
additional information and for those seeking technical information we
Those are the two I have personal experience with. Well, that is, aside from the one I live in (shameless plug) which is just getting started:
Dandelion Village in Bloomington, IN. We love visitors and often have couch surfers pass through. But right now we're three houses in a neighborhood attached to ~3 acres of land. We're just getting started building eco-houses and a food forest on the land. We spent about 3 years getting the city to change the land's zoning to allow us to build on it. Being in the city we've had to deal with a lot of regulations and politics, which just slow everything down. Also, sorry about the website. We're working on it!
If you want to find more, just do that google search and poke around the websites you find. You can learn a lot that way!