It's hard to describe DMT in one post, but I'll give it a go to provide you with some sense of it:
DMT is one of the most intense psychedelics available. It's short lasting, but the trip itself can feel like years. It comes from psychedelically active plants such as the bark of mimosa hostilis, but it has to be extracted in order to be available. I'm fairly sure that most of the plants that produce DMT are mostly found in the southern USA and rain forests in tropical countries. Extracting it is a process, and if you're completely unaware on how to do it, I would suggest you go out and try doing so (if you can even attain the hostilitis bark). It only becomes orally active when you mix it with an MAOI; this is usually referred to as ayuhausca.
Erowid can provide some more information:
http://www.erowid.org/chemicals/dmt/dmt.shtml
I highly doubt you would find this powerful, mystical substance at a rave. Typically raves have things such as molly and LSD to offer-- things that enhance the rave itself. DMT will pull you into hyperspace, an entirely different world, so it isn't really something suited for a rave. I also don't know how many people walk into a rave with the hardware necessary to smoke it.
There so much more to be said about it, but I hope this serves as an introduction for you. If you search for DMT on Bluelight, I'm sure you will be able to find a lot more information. Also, the DMT-nexus is a forum dedicated to the deemster.