You're on the right track already with John Holt!
Some resources that helped me when I was first thinking about homeschooling:
Growing Without Schooling magazine. It's not in circulation anymore,
, but you can get back issues here: http://www.fun-books.com/gws.htmHome Education Magazine
Anything by John Taylor Gatto.
Homeschooling For Excellence, by David and Micki Colfax. (This was the first book I read on homeschooling, and it really inspired me. I haven't read it in a long time, however, so I don't know what I'd think of it now.)
An excellent selection of general homeschooling books can be found at http://www.fun-books.com/homeschooling.htm.
Check out their whole catalog while you're at it.
I also recommend Rebecca Rupp's Complete Home Learning Sourcebook. It's not a general book, it's a huge book crammed with information on books, magazines, games, science equipment, computer programs, catalogs, web sites, curriculae, etc. etc. and divided into sections relating to what one's child might be interested. I took this out of the library when we were first thinking about homeschooling, and my husband and I spent hours pouring through it. There's just so much fun stuff out there! It's exciting!