5-MeO-DMT, which stands for 5-methoxy-n,n-dimethyltryptamine, is an extremely potent and intense psychedelic tryptamine. It's safety profile is pretty much like that of other psychedelics. Unlike it's illegal counterpart DMT, 5-MeO-DMT is not specifically scheduled (illegal) in the USA. However, its effects can be much more intense than DMT itself.
While DMT is more of a visual drug, 5-MeO-DMT is more of a "mindfuck" type drug. There are some visuals, but it is just basically like the universe imploding into your head, a huge mindfuck, which can be extremely scary or extremely blissful. The "place" where you go when you smoke it is often called The Void. This drug is the most common drug to cause ++++ (plus 4) experiences (see the Shulgin Scale in TiHKAL/PiHKAL). This drug will either make you shit yourself (not literally) in fear or give you an awesome blissful and transcendental experience (if you know how to handle it).
5-MeO-DMT is found in many natural sources, including many many plants and trees (There is usually DMT in the plant as well. Different species of different plants have different ratios/concentrations of these drugs). It is probably best known for being found in the Bufo Alvarius toad venom, along with 5-HO-DMT (AKA Bufotenine, which is not a pleasant psychedelic).
In its salt form, it can be snorted or injected. In it's more common freebase form, it is most often vaporized in a thin glass pipe, like methamphetamine. This leads to an intense psychedelic experience lasting 5-15 minutes, often accompanied by vomiting and muscle tremors. The dosage is 2-15mg in its freebase form. I would recommend starting your dose very low, so that you do not break through the first time. Also, ALWAYS make sure someone sober is with you and watching you (you move and shake a lot uncontrollably), ESPECIALLY if you do 10mg or more. Make sure your trip sitter grabs the pipe from you once you're done so you don't drop/break it.
Be careful, this is some crazy, crazy cosmic shit and only should be used by those with lots of psychedelic experience, in my opinion. Someone before me said that this drug is "foxy", which is actually 5-MeO-DiPT (which has EXTREMELY different effects, not even similar). It is not foxy, and if you get the two mixed up you will probably have a very, very bad experience.
My friend smoked 15mg of 5-MeO-DMT freebase to his dome the other day. Another friend of mine and I had to physically restrain him for about 5-7 minutes, all the while he had vomited on himself and was screaming swear words at the top of his lungs. The whole time, his whole body was shaking violently from muscle tremors and we had to keep him from hitting his head on the wall. Once he came out of it, he thought that he was laying on my bed in peace the whole time, having a great trip.