I'm really glad that you asked because there's a great article about it called Plants with Soul by Michael Posner which was published last year in the outstanding Canadian magazine "The Walrus." This is the best written, solidly researched and objective piece that I've read on a topic which is usually presented either foolishly or fearfully. It also tells the very interesting story of how the US Supreme Court decided unanimously that the anti-drug people could not prevent its use as a religious sacrament.
Here are the plants:
The leaf Psychotria viridis
and the vine Banisteriopsis caapi
Many traditions -- about 72 have been identified -- honor the sacred tea made from these plants, each according to their own religious narratives and ritual practices. The unique intelligence of plants is that they are the ones who know how to turn light into life. Thus, ayahuasca is considered by many as a "light unto the world" -- a powerful plant teacher and a guide connecting the stars of the firmament to life on earth.
Currently, some of the best exposition of the phenomenology of the ayahuasca experience can be found in the research of the cognitive scientist Benny Shanon. And, there's a lot more emerging from this well of wisdom. Stayed tuned.