I'd tell him to move to NYC for a gap year and work until he obtains residency. Then attend Hunter College or another CCNY campus for next to nothing as a NYC resident. If you're going to indulge him in leading his hip, romantic, non-conformist life, at least don't saddle him with too much student loan debt as he starts out. And certainly don't waste your own money on these pricey schools. Chances are, he'd be back living on your couch four years later, all tatted up with no place to go.

There's a book called, "Colleges That Change Lives" by a local writer, I think his last name is Pope. I haven't read it (I should get to it), but I think it lists a lot of the schools that have been posted here, like Macalaster and Oberlin, and describes campus life at these places.

St Johns College on Santa Fe

Swarthmore, Oberlin, Wesleyan, Reed, Pomona, Grinnell

Bard

3rd for Reed.

Cornell (re: 10:31's point -- Yeah, sort of. But while there may be a boho element at UVa, there's a whole lot more crunch going on at UMich or UWisconsin or Berkeley)
Haverford
Oberlin
Reed
Hampshire

Antioch College

Any big college will have some subset of students (and profs), as well as programs and activities that will inspire your DC.

My nephew, who sounds like your DS, ended up at Bard. He also applied to Kenyon, Oberlin, Reed, Brown and (I think) Brown.

Thanks for the ideas, which mostly track with what I was thinking. (What about Bard? Sarah Lawrence?) He is a self-starter so he doesn't need to have a lot of structure but it is important that he be in an academically rigorous school.

Ditto Oberlin

UC santa cruz

Anywhere in California?

Evergreen State College, Olympia WA.

Macalaster College, St. Paul MN

Univ. of Wisconsin-Madison

Univ. of Santa Cruz (CA)

Kenyon


[and all the other great ideas already posted]