sleep deprivation - I get all manic and speedy by about 5 AM if I'm sober (used to stay up editing magazines from time to time), very giddy too in a way that stimulants don't do. Absolutely terrible for the body though, I feel wrecked for 2 days. Worse than anything I've done except high doses of AMT and the worst hangover I ever had.
dancing - I almost feel like I "trance" when I'm dancing sometimes - I just feel like a giant energy hose. Usually when I'm in the zone it gets a big response from women, who start dancing very close, and people who are with me and are insecure about their dancing skills get intimidated. I can pretty much do this at will at this point, hip-hop, techno, rock, whatever, but I don't very often because most of my friends are white-bread types who can't feel the beat and they think I look funny and keep trying to get me to slow down and sort of squirm all detached-like. I do a lot better at clubs with a largely african-american or raver crowd, because most of the people can feel the beat.
music - I was sober at one of the phish shows I attended this summer, and all I remember about the big jam of the second set, and in fact all I could remember about it as it was ending, was "it was mostly white and came back in on itself twice." Sweet jesus.
breathing/mantra meditation - I got pretty good at this, it'll match up to any mid-plateau dissociative in the book as far as getting out of the body. This is the easiest high that I've had that I could bottle and sell, because you're just *gone* in a pleasant bliss. I stopped doing it because it was too much like a drug and I realized I was using it to escape rather than deal with my situation.
awareness meditation - I usually wind up containing some of my current ego constrictions in a much, um, larger and lighter space than I'm used to. I don't know if I would call this "high," though.
kensho - I don't expect that you'll believe yet another random net poster, but I had the full flash. Not high per se, just as it is. I was, like I have always been and all of you are, the eternal "nothing," beyond time and space and at the same time this body. Then some of the old ego constrictions started back up. But I can never turn my back on it, and it's had by far the most impact of any one experience on how I see and behave in reality. Unbelievably frickin frightening (or was that just a giant energy release?) as it was coming, despite years of previous work and experience in expansive states.
religion - Never got the buzz from being in church myself, but I think I can understand it, it's like being in a crowd that's really into it at a rock concert in some ways. It's an energy release that lifts people temporarily outside some of their constrictions, so they experience the eternal clear light at the basis of reality (call it god?), or a slightly restricted and dimmer version thereof. Sincere, fervent prayer helps to generate the energy as do building structures, collective focus, lighting, music, etc. As people come back out they can use this energy and perspective to improve themselves, work through their emotional blockages and hatred, and become better people. If they don't want to do that then they can use the energy to further strengthen their constrictions to an unbalanced extent, just like any other method. Which is why a lot of fundamentalists, just like a lot of meditators or drug users, seem so unbalanced, especially because most ministers don't have a particularly clear idea of what they are working with and couch a lot of their speeches in conversion rhetoric rather than peace. The fundamentalist churches are currently growing and growing because mainstream churches are just dishing out lectures on morality and don't understand the energy at all.
oh, and how could I forget orgasm, duh.
whoever was thinking about sleep deprivation, definitely read up on it at erowid. there are a couple of people who really fucked themselves up badly, esp once you go through a second night. Not necessarily safer or more interesting than drugz at all.