Is there a form of Buddhism without Rebirth?
I am pretty much an atheist but I would like to go down the "path of enlightenment". I want to study something that cuts out all supernatural/god/afterlife teachings. Is Zen Buddhism the closest thing I will find?
Are there other philosophies/spiritual teachings that would be better suited for me (even outside of Buddhism)?
Zen Buddhism is very close to Taoism, in fact there's a book called the Tao of Zen, you may want to read. Taoism in it's original form contained no concept of any imaginary lives after this one. It is about be here now, like Zen, no goofing off!
Hinayana Buddhism (the lesser vehicle) is also free of superstitious barnacles like afterlives. The Pali Canon is your best source. It's just some old long oval leaves of paper with the words of the Buddha on them. The Dhammapada is there.
Atheism is the beginning of the true spiritual search. Seekers should start out without the answers, instead of with them.
Alan Watts is the teacher I would recommend first. After him, Stephen Gaskin (see The Farm in Summertown TN -- see Sunday Morning Sermons on the Farm, published by The Book Publishing). Stephen is well schooled in the Vedas, particularly Rig Veda, Diamond Veda, and Heart Veda -- I go to his words when I want to know about those things.
Ecknath Easwaran -- the best translator and commentator on the Upanishads and the Gita -- again his books are published by his Center for Meditation in California.
I also have profound respect for the Maharishi Mahesh Yogi. He has done a translation of the Bhagvad Gita -- He was the teacher of the Beatles. He had the wondrous quality of not being a prude or a prissy sort. He loved pleasure and anything that gave pleasure which did no harm to others. He did not have a Calvinistic sufferring oriented approach to spritiuality -- self-denial equals holiness. He was more along the lines of Omar Khayyam or Hugh Hefner or Timothy Leary -- Go ahead -- have a blast -- just don't hurt anybody else. Originality bespeaks greatness in a teacher. The Maharishi was one of a kind. He was truly a Maha (great) Rishi (teacher).
For Buddhism -- you want Watts. He was a student of Christmas Humphries and the London Buddhism Center, and later of T.D. Suzuki. He was ordained, but then left the priesthood. He lived on a tugboat in Sausolido. He wrote many books, and also made tapes, and videotapes. He's a charming teacher.
Also see Philip Kapleau Roshi who is famous for saying, "All life is life after death". Philip is a Zen Buddhist I think. He studied in Japan for 30 years.
Also see the Advaita School of Hinduism advocated by Shankara. Thou art that -- Tat Tvam Asi -- the distinction between what you are and what is not you, is an illusion -- there is really no such distinction -- you are starstuff -- not just a creature made of former starstuff -- a existent that is at one with the starstuff out there right now.
I studied in China, to become a Juin-Tze, or teacher of Taoism. There, they call me Gao Bwo Fu.
To my mind, the important book on Zen Buddhism is 'Zen Mind, Beginners Mind' by Shunryu Suzuki.
But also investigate the 'spiritual' tradition that starts with Socrates.
And, you can make up your own. Borges said: Every artist (but why not person) creates his own tradition.